How To Prove Cell Tower Identification In Court

Transcription

1 49 NO 3 CRIMLAWBULL ART 8 Page 1 Criminal Law Bulletin Summer 2013 Volume 49, Issue 3 Criminal Law Bulletin The Use of Global Positioning ( GPS) and Cell Tower Evidence to Establish a Person's Location Part II James Beck, Christopher Magana & Edward J. Imwinkelried[FN*] This is the second article in a series. The first article, which appeared in the January-February 2013 issue of this journal, discussed the use of global positioning system ( GPS) evidence to determine an accused's position at the time of the actus reus. After reviewing GPS technology and the underlying science, the article addressed the question of whether the use of GPS technology to determine a person's location their latitude, longitude, and altitude satisfies the Daubert reliability test for the admission of expert testimony. The first article concluded that the use of the GPS technique for that purpose satisfies muster under restyled Federal Rule of Evidence 702. The article added the caveat that in some cases in which the GPS device requires manual input of data for one or more variables, the opponent might be able to exclude the evidence under Rule 702(d). However, in the vast majority of cases an expert can accurately determine a person's by employing GPS technology. The first article indicated that the next article in the series this article would turn from GPS technology to a related subject, that is, the use of cell tower evidence to determine a person's location. Like the prior article, this article initially describes cell tower technology and the underlying science. This article points out that while courts and commentators sometimes refer to cell tower evidence in the singular, in truth there are several different cell tower techniques for determining a caller's location. After differentiating among those techniques, the article takes up the question of which, if any, of those techniques satisfy the Daubert standard. The article demonstrates that courts should pause long and hard before admitting testimony based on the most commonly used technique, namely, cell identification. I. INTRODUCTION It is 3:00 a.m. on a dark and stormy night, and the operator at the 911 center has just received a call from a distressed individual using a cellular telephone. The frantic caller tells the operator that he has just been involved in a car crash and that a passenger needs immediate medical attention. Please give me your location, I'll dispatch an ambulance immediately, the operator says. The caller, disoriented from the crash, looks around for a street sign or some other indication of his location to provide to the operator. However, he sees nothing helpful. Panicked, he informs the operator that he, the caller, has no idea where he is. That's okay, says the operator. Stay calm. We'll find you. In 20 minutes an ambulance pulls up alongside the caller's vehicle. Emergency personnel immediately tend to the passenger's injuries. No lives are lost, and disaster is averted. How did the ambulance find the caller with absolutely nothing to go by? Magic? Luck? No. It was science. Thanks in large part to advances in technology, with a gentle push from the federal government,[fn1] 911 operators can quickly determine the approximate location of a caller using a cellular phone to within meters. By using the data generated when the caller connected to the 911 center, the operator was able to provide the ambulance service with the caller's approximate location. Using the known locations of two or more cell phone towers and the amount of time it took for the cell phone's signal to reach those towers or the angle at

2 49 NO 3 CRIMLAWBULL ART 8 Page 2 which the phone's signal hit the cell towers, the operator could readily determine the caller's location. In its simplest form, this is called triangulation, a technique that has been used in navigation for centuries. It is tried and true. And, most importantly for the caller and his injured passenger in this scenario, the technique is accurate. But vary the scenario. In this variation, there has been a shooting at the Kwik-E-Mart. Apu, the clerk, was shot in an attempted robbery. After interviewing Hans Moleman, an eyewitness to the shooting, the police determine that the attempted robber was likely a local criminal nicknamed Snake. The police find and arrest Snake at Moe's Tavern, one of his known haunts, where he is drinking with friends. At the subsequent trial, prosecutors seek to corroborate Mr. Moleman's eyewitness testimony by introducing the call data records generated by Snake's cell phone the night of the attempted robbery. In court the prosecutors offer a map of Springfield with all the cell phone towers in town. The prosecution also submits a PowerPoint presentation, using a red dot to represent Snake's cell phone. Each time the phone connects to a new cell tower, a ping sound goes off; and the area covered by that tower flashes. The jury watches as the red dot moves across town from cell tower to cell tower, starting with one covering the Kwik-E-Mart at the time of the attempted robbery and ending at a tower covering Moe's Tavern at the time of Snake's arrest. The PowerPoint presentation seems to be powerfully incriminating evidence. However, the critical question[fn2] for Snake's attorney is whether, in this variation, the prosecution is using the same science as the 911 operator employed in the first scenario. In truth, there are several different cell phone techniques for determining a caller's location; and the two variations involve two very different techniques. As in the second variation, prosecutors frequently use the cell identification technique based only on one or more call detail records provided by the cell phone network carrier.[fn3] This technique is vastly inferior to the more accurate triangulation technique employed in the first scenario. This article will demonstrate that the cell identification technique can be used only to establish that a caller was within the coverage radius of the cell tower used during a given communication.[fn4] While the technique employed in the first scenario justifies an inference as to the caller's location, the cell identification technique supports a much weaker inference that the caller was within a coverage area that can be quite large. II. CELLULAR PHONE NETWORK TECHNOLOGY AND THE UNDERLYING SCIENCE In order to understand how cell phone data can be used to track an individual, it is important to appreciate how cell phones work. Cellular technology makes use of radio waves to carry transmissions back and forth between a mobile unit (e.g., a cell phone) and equipment at a cell tower that, in turn, is connected to the wired telephone network. Every time a cell phone connects to a cell tower, valuable information, such as the time and date of the call, is collected and stored by the cell phone company. Companies collect this information for a number of reasons, including for billing, to monitor traffic on their network, and to aid in planning future improvements of their service. Upon a request by prosecutors or investigators, the cell phone company draws on this information to generate a record of the longitude and latitude of each tower that a user's cell phone connected with during a cellular communication. This information can be used to help determine a caller's location during the call. The information includes data about both the network the cell phone connected to and the cell phone making the connection. A. Network Setup that the Phone Connects to Like conventional radio and television broadcasts, a cellular communication is a transmission on the radio frequency spectrum. The available frequencies, licensed in the United States by the Federal Communications Commission (FCC), are limited. Cellular networks work around this limitation by transmitting signals at a low power so that frequencies can be reused multiple times in a small area.[fn5] (In contrast, radio and TV broad-

3 49 NO 3 CRIMLAWBULL ART 8 Page 3 casts transmit their signals at a high power to cover as large an area as possible, roughly 100 miles in radius.)[fn6] In order to provide wide coverage by using low power broadcasts, cell networks use numerous base stations, located at the base of cell phone towers. These base stations create small cells where a particular frequency can be used by a single user. The more cells there are, the more cellular communications that can be serviced at any given time. The number of base stations and relative distance between them vary and are determined by the network carrier largely based on the demands on the network. Base stations are more numerous and densely packed in urban areas, where demand is high, than in rural areas, where demand is typically lower. Cell phones communicate with the base stations. In turn, the base stations communicate with a system controller, which oversees the operation of an entire network in a given region.[fn7] When a cell phone leaves one cell and enters another, the system controller assigns a new frequency to the communication between the cell phone and new base station.[fn8] System controllers are connected to the traditional wired telephone network service, permitting communication between cellular and landline phones. Although the terms cell and cell site are often used interchangeably, there is a fundamental difference between the two. Cells represent the geographical area covered by cellular radio antennas. When they are mapped out, cells are depicted as hexagons.[fn9] In contrast, a cell site does not denote a geographical coverage range; rather, it is a fixed location that provides radio coverage to a cell. A cell site is typically situated at a corner edge of a cell where that cell aligns with two other hexagonal cells. The physical equipment the antennas, base station, and other network equipment are located at the cell site. Each cell can be covered by a single cell site, but the cell is more typically served by three different cell sites. If a cell site uses omnidirectional antennas and is located in the center of each cell, the cell site can service an entire, 360 area. More commonly, though, a cell site is located at the edge of three hexagonal cells. These cell sites are equipped with three directional antennas, and each antenna faces inward toward a different cell. As a result, each of the three antennas at a cell site ordinarily covers 120 of one of the three separate cells. The precise area covered by a cell site depends on a number of factors, including the height of the tower and topography.[fn10] In urban areas, a tower's signal radius is usually two miles or less.[fn11] In particularly dense urban areas, the signal radius might be only a few hundred feet.[fn12] In rural areas, the radius is much greater, often around nine to ten miles.[fn13] B. The Cell Phone Connecting to the Network How does a cell phone connect to a particular cell site? At a later point in time what documentation of the connection can the cell phone company provide? Registration A cell phone registers with a cell site. Every time a person turns on a cell phone, the phone periodically transmits a signal that is received by every antenna tower within range of the phone.[fn14] This is the cell phone's way of telling the network that it is in the service area and is ready to make and receive calls. Even after a phone has been turned on, this registration signal is sent roughly every seven seconds, whether or not the phone is engaged in a call.[fn15] The phone continues emitting the signal so that as the user moves from one cell to another, the network can service calls to and from the user's phone. The phone's registration signal contains important information including each phone's Electronic Serial Number (ESN) and Mobile Identification Number (MIN).[FN16] The ESN is an identifying number that is

4 49 NO 3 CRIMLAWBULL ART 8 Page 4 unique to every cell phone indicating the manufacturer and the serial number assigned to the device.[fn17] Although it is possible to change the ESN of a cell phone, the change requires extensive computer knowledge (and is classified as a felony under United States law).[fn18] The MIN is the ten-digit phone number assigned to the phone.[fn19] The only way to stop a cell phone from emitting registration data is to block the radio signal either by placing it in a shielded container or by switching the phone to Airplane Mode. [FN20] Cell Detail Records (CDRs) Documenting Registration and Other Information In addition to recording registration data, cell phone companies collect and store what are usually referred to as Call Detail Records (CDR). These records are compiled to enable the provider to accurately bill a subscriber for his or her cell phone usage.[fn21] The records are also used for other legitimate, innocuous purposes, such as helping carriers understand the calling patterns of their subscribers. Information about calling patterns helps the carriers determine what upgrades are needed to their network.[fn22] When a call is made from or made to a cell phone, a mobile switch within the phone selects the cell site with which it has the strongest connection to establish a registration. Due to a number of factors, including topography and call volume, that tower is not always the closest tower to the cell phone.[fn23] CDRs are collected and stored by equipment at the cell site's base station when a phone connects with an antenna.[fn24] The records include: the ESN, the MIN, the number of the phone at the other end of the communication, the date, start and end times of the call, and the identity of the tower to which the phone connected.[fn25] The cellular service providers retain CDRs for various periods. According to a document prepared by the U.S. Department of Justice, all major providers retain CDRs for at least one year; and some providers retain them indefinitely.[fn26] Cellular companies use this information for business purposes, but they sometimes make this information available to law enforcement authorities to help the police place a cell phone user in a particular location at a particular time sometimes the site of the actus reus of a suspected crime.[fn27] III. CELL TOWER TECHNIQUES FOR DETERMINING LOCATION, INCLUDING THE CELL IDENTIFIC- ATION TECHNIQUE There are four basic categories of techniques used to track the movements of a cellular phone: handset-based, network-based, a hybrid of the two, and finally SIM-based. Handset-based techniques involve a GPS chip or other similar technology installed in the cell phone itself that generates location data.[fn28] The first article in this series discussed GPS evidence in detail. As that article indicated, the more modern cellphones include GPS chips. Network-based location data are ascertained by analyzing a cell phone's wireless signal in relation to nearby cell sites.[fn29] Like the handset-based technique, network techniques can be used to track a phone in real-time or to create a historical record of a cell user's location. As the name implies, hybrid techniques use data generated by analyzing both the GPS device in the handset and the cell phone's wireless signal. Popular smartphone applications like Yelp employ this technique to identify an individual's location in order to provide a list of nearby business. Finally, SIM-based location techniques involve accessing the phone's SIM card and analyzing the raw radio measurements stored on it while the phone is in service.[fn30] This technique may be useful in retracing a user's location, but the technique requires physical access to the cell phone and removal of the SIM card. For that reason, the technique is not useful in real-time tracking.

5 49 NO 3 CRIMLAWBULL ART 8 Page 5 The focus of the remainder of this article is the use of network-based tracking to establish a cell phone user's location. It is true that in 2011 nearly 80% of cell phone units shipped came equipped with a GPS device.[fn31] However, a large number of non-gps equipped phones are still in use, and to date in the majority of the judicial decisions that have involved the use of cell-phone records, prosecutors have relied on networkbased tracking to establish a suspect's location. There are four network techniques: cell identification, angle of arrival (AOA), time of arrival (TOA), and time difference of arrival (TDOA). A. Cell Identification Cell Identification is both the easiest location method and the cheapest to implement.[fn32] Unfortunately, it is also the least accurate network technique. Even when an expert properly uses the technique, the technique can only pinpoint a user's location to within 100 meters to 3 kilometers.[fn33] The technique uses two end points, the cell phone and the cell site, in an effort to determine which cell the user was located in at the time of the call.[fn34] This technique serves the cell phone company's basic need of identifying which cell a user is in so that the system knows which cell site to use to process the user's communication. The technique was not designed as a means of placing a caller at a fixed location (i.e., longitude and latitude) at a given time.[fn35] Call Detail Records identify the tower used to process the call, and will often indicate which antenna on the tower serviced the call. Knowing the coverage area of the tower or, better still, the smaller coverage of the antenna, an expert can infer that the user was within that geographic coverage area at the time the call was placed.[fn36] For example, if the CDR indicates that Tower XYZ was used to a service a communication between a suspect and another party at 2:00 a.m. on March 18, 2013, it would be assumed that the user was in the coverage area of that tower at that time. The problem is that this coverage area can be extremely large, especially in rural areas. If Tower XYZ is an omnidirectional tower (located at the center of a cell and sending signals outward) with a radius of 12 miles,[fn37] the total area of coverage would be roughly 452 square miles.[fn38] At most, a proponent of the evidence could argue that the evidence shows that the user was somewhere within this zone.[fn39] That is the only necessary inference from the cell identification technique. Keep in mind that a city the size of San Francisco is only 49 square miles. As one can imagine, this technique is not very helpful in placing a user at a particular crime scene at a specific time. The evidence may have little incriminating value when the user lives in the coverage zone or has other legitimate reasons for being in that geographical region. Suppose that the cell site was located at the intersection of three cells and was equipped with three antennas directed inward toward each cell, thus reducing the coverage zone from 360 to 120. Even on that supposition, the coverage area would still be too large to be of much use in locating an individual. Assuming that each antenna covers closer to 160,[FN40] each sector of a cell site with a radius of 12 miles covers just over 200 square miles.[fn41] While the large geographical area that a single cell can cover diminishes the probative value of the cell identification technique, perhaps the biggest drawback of the technique is that cell phones can be associated with cell sites that are not even in close physical proximity.[fn42] Again, cell phones connect to the cell site with which it has the strongest signal. Even if there was a cell site in closer proximity, for a number of reasons that site may have been unavailable to service the cell phone. Among the factors affecting which cell site a phone connects with are: (1) the number of available cell sites; (2) whether maintenance or repairs are being performed on a given cell site; (3) the height of the cell tower; (4) the height and angle of the antennas on a cell tower; (5) the range of coverage; (6) the wattage output; (7) the call volume at any given time and the call capacity of a cell cite; and (8) environmental and geographical factors such as weather, topography, and the density of physical structures

6 49 NO 3 CRIMLAWBULL ART 8 Page 6 in the area.[fn43] Given these factors, it can be very difficult to locate an individual within a particular cell, especially if that person is in a multi-story building where there is often considerable cell overlap from one floor to the next.[fn44] Due to the limitations of cell identification technique, a better technique for locating an individual's precise location involves using angulation or a form of lateration, which will be addressed in the next three subsections. B. Angle of Arrival (AOA) In the Angle of Arrival (AOA) method, a mobile device is located by determining the angle of arrival of the radio signal at the receiving sensor at the base station.[fn45] Two or more receiving sensors are required for this technique.[fn46] The principles underlying this technique have been used in navigation for centuries. The technique is still employed in aircraft navigation today.[fn47] AOA is a form of triangulation that should be familiar to anyone who took geometry. The location of a cell phone can be determined by using the known angle of arrival of a signal from cell phone X at cell sites A and B. Cellular companies know the distance between cell sites, and the angle of arrival at the site can be determined by equipment at the base stations. This data are then used to locate the phone.[fn48] The problem with terrestrial applications of the technique is that radio waves require a clear line of site between the cellular user and the cell sites in order to accurately determine the user's location.[fn49] The technique is accurate in airplane navigation in the skies where there are fewer obstacles to obstruct a radio signals path. However, on land, topography and man-made structures can affect the accuracy of this technique. On land, the technique is generally accurate in locating cell users from between 100 and 200 kilometers.[fn50] On land in dense urban areas, AOA is practically unusable because there is rarely a direct line of sight to two or more base stations.[fn51] C. Time of Arrival (TOA) Like AOA, the Time of Arrival (TOA) technique uses two or more cell sites to determine the location of a cell phone user. Instead of measuring the angle of arrival of a radio signal, TOA measures the distance the radio signal traveled between a cell phone and a cell site.[fn52] This technique makes use of what geometry students know as DiRT: Distance = Rate x Time, the same formula discussed in the first article in this series. As the first article explained, knowing two values, you can compute the third variable in the formula. Radio signals travel at roughly the speed of light (299,792,458 meters per second). Hence, the distance between a cell phone and a base station can be determined from the elapsed time it takes for the signal to travel between the phone and the station.[fn53] The distance between the phone and a particular cell site is used as the radius to create a circle around each cell site.[fn54] The cell phone can be located at any point on the circumference of this circle.[fn55] That information obviously has very little value in determining the location of the caller at the time of the call. It is therefore necessary to construct additional circles around other cell sites, representing the distance between the phone and those sites. The user is located at the point where the circles intersect.[fn56] The more cell sites with which the mobile unit connects, the more accurately the user's location can be determined.[fn57] TOA is accurate in locating a cell user to within meters.[fn58] One of the challenges to TOA is that it involves the use of absolute time: in order to yield an accurate determination of location by using TOA, all the receiving sensors as well as the mobile device must be synchronized with a precise time source such as an atomic clock.[fn59] If the clocks are off by even 100 nanoseconds, an error of 30 meters can result.[fn60] Equipment failure can render the location determination inaccurate, as

7 49 NO 3 CRIMLAWBULL ART 8 Page 7 can signal noise and physical obstructions.[fn61] TOA does not require a direct line of sight like AOA, but the TOA still works best in open areas.[fn62] D. Time Difference of Arrival (TDOA) The Time Difference of Arrival (TDOA) technique is similar to the AOA method in that the technique measures the distance the radio signal travels between the cellular unit and three or more base stations. However, unlike AOA, TDOA uses relative time instead of absolute time: Only the time at the base stations need be synchronized with one another.[fn63] Of the four techniques addressed, TDOA is the most accurate method and can yield results of a user's location within less than 50 meters.[fn64] Locating a phone by using TDOA involves the mathematical concept of hyperbolic lateration. The difference in the time of arrival between the cell phone and cell site A and the time of arrival between the cell phone and cell site B is calculated to produce a hyperbolic curve.[fn65] The points along the curve represent all the possible locations of the cell phone.[fn66] To narrow the location of the cell phone, a second hyperbola is added to the picture by taking the difference in the time of arrival between the phone and cell site A and the time of arrival between the phone and cell site C.[FN67] The intersection of the two hyperbolas indicates the general location of the cell. More cell sites can be added to specify the size of the location.[fn68] The principal advantage of TDOA is that it does not require clock synchronization between all the endpoints; only the cell sites need be synchronized. However, like TOA, a discrepancy of 100 nanoseconds between those sites can result in errors of 30 meters.[fn69] TDOA is also susceptible to the same types of interference that affect the accuracy of TOA; both techniques are vulnerable to such interferences because they both rely on radio signals to measure distance.[fn70] IV. THE ADMISSIBILITY OF CELL TOWER EVIDENCE, INCLUDING TESTIMONY BASED ON THE CELL IDENTIFICATION TECHNIQUE As of 2010, 89% of the total population in the United States owned a wireless phone.[fn71] Given this high percentage, the likelihood that call data records will find their way into a courtroom in the future is increasing. Given the wealth of information that call data records contain and their obvious relevance in criminal investigations, the number of cell tower evidence cases is increasing rapidly;[fn72] and some commentators have gone so far as to call cell phone evidence the new DNA. [FN73] DNA has come a long way since it was first introduced as the new fingerprint. Early iterations of DNA testing were not as accurate as modern techniques, in part due to technological limitations. At present, there are limitations to the use of call data records to establish a suspect's location; but, in the case of cell tower evidence, the limitations are not due to technological problems. Rather, the limitations are largely attributable to business decisions by cell phone companies. Despite the greater degree of accuracy of the AOA, TOA, and TDOA techniques, in most cases today prosecutors cannot use those techniques. They cannot do so because the call data records maintained by the companies ordinarily do not contain the data necessary to use those techniques.[fn74] For example, the companies see no business reason to maintain data about the angle of arrival or the distance the signal travelled between two or more towers.[fn75] However, the companies do perceive a business reason to collect the time, date, duration of a call, and the first and last cell site used all of which are necessary to use the cell identification technique. Of course, that business reason relates to customer billing. As a result of the companies' business decisions, in the typical case cell identification is the only technique that can be used to create a historical record of where a cell phone user was at a given time. The companies' call data records contain the information necessary to use that technique but not the other, more accurate, methods of determining a caller's location.

8 49 NO 3 CRIMLAWBULL ART 8 Page 8 If a proponent decides to offer cell tower evidence, the proponent will face three hurdles. The proponent must convince the trial judge that the data is (1) relevant under restyled Federal Rules of Evidence 401 to 02, (2) the witness is qualified under Rule 702, and (3) the technique employed by the expert qualifies as reliable scientific knowledge under Rule 702(a). A. The Relevance of the Data under Federal Rule of Evidence 401 Federal Rules of Evidence 402 announces that all [r]elevant evidence is admissible except as otherwise provided by law such as by federal statute.[fn76] Rule 401 defines relevant evidence as evidence having any tendency to make a fact more or less probable than it would be without the evidence. [FN77] Even if the cell identification technique can only place a cell user in a larger geographic coverage region at a particular time, the information can be relevant under the Rules 401 and 402. For example, suppose the prosecution claimed the accused was near the scene of a crime that occurred at 3:00 pm on 5 th Street and Russell Boulevard in Davis, California. If the cell user claims he was in Plano, Texas the day of the crime, call data record evidence indicating that his phone was served by cell sites in Plano would certainly be relevant to his alibi defense given that the evidence tends to show that he was in Texas and, consequently, could not have committed the crime in question. (Of course, this defense argument assumes that the accused was the person using his cell phone, which can be a separate issue.) It gets trickier when the accused was in the same town at the time of the crime and the cells are much closer to each other. However, the call data record still has some probative value because the contents of the record can make the accused's presence in the area (and ability to commit the crime) more or less probable than it would be without the evidence. Even if the evidence satisfies the requirements of Article IV of the Federal Rules, the evidence must still run the gauntlet of Article VII. Under the provisions of that article, the proponent of the evidence must establish both the witness's status as an expert and the reliability of the technique that the witness utilized to generate his or her inference. B. The Witness's Qualification as an Expert Under Federal Rule 702 The courts have been all over the map[fn78] regarding the qualifications of the prospective witness who may testify about the interpretation of call data records and the application of the cell identification technique. At trial, the prosecution typically calls two witnesses to establish the accused's location based on Cell Identification.[FN79] The first witness is usually an employee of the cellular company, and the second witness is ordinarily an agent from the FBI or other law enforcement agency.[fn80] One might think that a witness testifying about the cell identification technique would need to be an expert familiar with the science underlying cellular networks, but some jurisdictions permit witnesses to testify based on their experience and specialized knowledge of the technique.[fn81] Yet, some courts have accepted lay testimony related to cell tower tracking.[fn82] However, many of these courts tend to limit the testimony by lay records custodians to general information about how to interpret phone records and how the records reflect cell sites.[fn83] By way of example, in Wilson v. State, the expert from the cellular company had no formal training or background in the science of cellular networks.[fn84] In fact, she admitted on the stand that she lacked any specialized knowledge in cellular technology or corresponding theories.[fn85] However, she was allowed to testify as an expert because of the following: her job duties included interpreting customer records to determine the location of cell sites that acquired the call signals; she had four to six months of training from her employer in electronic surveillance; and she frequently assisted law enforcement in tracking defendant's movement.[fn86] Although the witness had some experience with the technology at issue, it is surprising that the court permitted her

9 49 NO 3 CRIMLAWBULL ART 8 Page 9 to testify as an expert when her knowledge of the science underlying cellular networks was virtually non-existent. In contrast, when the witness's proponent seeks to elicit the witness's estimate of the caller's location at the time of a particular call, courts tend to demand that the witness qualify as an expert.[fn87] In the published opinions, both law enforcement officers and cellular company employees other than mere records custodians have qualified as experts.[fn88] In some cases, though, courts have been rather lax in evaluating the alleged expertise of the law enforcement witness typically called by the prosecution.[fn89] Frankly, in several reported opinions, the officer's experience and training in cell identification have been relatively shallow. Saenz v. State is a case in point. In Saenz, a Texas state court sustained the admission of testimony by a police officer with only four years of experience on the force. The officer had attended a three day course in cell phone tracking, and had used the technique on only 12 prior occasions before giving an opinion, based on the interpretation of the call data records, placing the accused in the general vicinity of the crime.[fn90] In Kumho, the Supreme Court made it clear that a witness's practical experience can qualify the witness as an expert. It could be argued that treating witnesses like the cell phone employee in Wilson and the detective in Saenz as experts is consistent with the liberal spirit of Kumho. However, there is a strong counter-argument. It is conceivable that an individual without formal education or training could acquire enough knowledge about the relevant science to assist the trier of fact in understanding the significance of the data in call data records. However, in the published opinions, courts did not demand any showing of the witness's mastery theoretical or practical of the pertinent scientific principles and techniques. As Part III of this article demonstrated, the cell identification technique rests on principles derived from science rather than informal experience. If so, to qualify as an expert on the use of the technique, a witness should possess some, minimal familiarity with those principles. C. The Reliability of the Expert's Technique under Federal Rule 702 Before admitting expert testimony, a trial judge must determine that the testimony is not only relevant but also reliable and of assistance to the trier of fact in understanding or determining a fact in issue in the case.[fn91] This is the core takeaway from Federal Rule of Evidence 702, which mandates the exclusion of expert testimony unless the judge finds that (a) the expert's scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue; (b) the testimony is based on sufficient facts or data; (c) the testimony is the product of reliable principles and methods; and (d) the expert has reliably applied the principles and methods to the facts of the case.[fn92] In essence, Rule 702 tasks the trial judge to serve as a gatekeeper to assure that all expert testimony is not only relevant but also reliable.[fn93] As the first article in this series noted, to aid judges in performing their gatekeeper function, the Supreme Court in Daubert v. Merrell Dow Pharmaceuticals listed five factors that trial judges should consider. Although the Court stressed that these factors are neither dispositive nor exhaustive, [FN94] they are considerations that the judge should weigh at least when the proffered expert testimony is purportedly scientific. In particular, the trial judge ought to weigh whether: (1) the scientific theory or technique can or has been tested; (2) the theory or technique has been subjected to peer review and publication; (3) the technique has a known or potential known rate of error; (4) there exist operational standards for controlling the technique's operation; and (5) the theory or

10 49 NO 3 CRIMLAWBULL ART 8 Page 10 technique has gained general acceptance.[fn95] In relatively short order, the Supreme Court's 1993 Daubert decision was followed by two Supreme Court cases clarifying the types of evidence subject to Daubert-style reliability scrutiny and the nature of the scrutiny. In 1997, the Court rendered its decision in General Electric Co. v. Joiner. There the Court held that a trial judge may reject an expert's testimony when there is simply too great an analytical gap between the data and the opinion proffered. [FN96] In 1999, in Kumho Tire Co. v. Carmichael, the Court extended Daubert's requirement for a showing of reliability to all types of expert testimony, whether scientific, technical, or specialized.[fn97] In retrospect, the Kumho Court recognized that the factors listed in Daubert were derived primarily from the classic scientific model. In that light, the Kumho Court acknowledged that those factors might be inappropriate for the evaluation of non-scientific expertise. However, the Court made it clear that whatever type of expertise the witness relies on, the trial judge cannot accept the witness's ipse dixit assertion that his or her technique is reliable. In all three cases in the trilogy, Daubert, Joiner, and Kumho, the Court has made it clear that the proponent must establish the empirical validity of the specific theory or technique that the expert contemplates relying on.[fn98] In that light, suppose that the expert's proponent is not content to elicit testimony about the general manner in which cell towers operate.[fn99] Instead, the proponent wants to adduce expert testimony estimating or even pinpointing the caller's location at the time of a particular call.[fn100] As Part III explained, given sufficient data, an expert may validly use the angulation or lateration techniques of AOA, TOA, or TDOA to determine a caller's location at the time of a call. Those techniques rest on validated, widely accepted scientific principles. However, as Part III also noted, in most instances, including the published opinions, the prosecution's cell tower experts do not invoke those techniques. Rather, because of the limited data included in cell phone companies' records, the experts rely on the cell identification technique. The question is whether that technique satisfies Daubert. Just as the first article in this series applied the five Daubert factors in detail to GPS evidence, this article will apply the same factors to assess the admissibility of cell tower evidence based on the cell identification technique. Whether the scientific theory can be or has been tested There are scientific principles governing the behavior of radio waves. The angulation and lateration methods of AOA, TOA, and TDOA rest on those principles. However, the cell identification technique rests on additional assumptions. Cell phones are designed to connect to the cell site with the strongest signal. That site might or might not be the closest site. Even if a cell phone registered with a particular site, the witness cannot assume that that was the closest site to the accused; nor can the witness draw that inference from the datum that the caller's phone connected to a particular site.[fn101] When a proponent offers cell tower evidence, judges need to probe more deeply to identify the following: (1) the technique the expert is relying on; and (2) the inference the expert wants to draw. Concededly, the science behind radio waves has been researched and tested for decades. It is true that in a general sense, the expert is drawing on that body of well-accepted science as a basis for his or her testimony. However, standing alone that science does not support the inference the expert proposes testifying to about the caller's location. Rather, the expert must always rely on a more specific technique. The validity of the science of radio waves does not dictate the conclusion that the cell identification technique is valid. Moreover, even positing the validity of the cell identification technique, a trial judge should not permit an expert, relying on this technique, to opine that the

11 49 NO 3 CRIMLAWBULL ART 8 Page 11 caller was at a specific location at the time of the call. At most, the proper use of the cell identification technique enables the expert to conclude that the caller was within a more or less large geographic area at the time of the call. For that matter, even that modest conclusion may be debatable. Manfred Schenk, an expert on cell phone communications, has appeared as a defense witness in several cases. At several trials, he has testified that even if the use of the cell identification technique supports an inference that the accused was in a particular tower's coverage zone, it is impossible to determine where the call was located within that area. Moreover, he has testified that it is impossible to (1) positively identify which cell phone tower was used by a caller or (2) know whether a particular call was actually routed to a specific cell tower.[fn102] In United States v. Evans,[FN103] the expert proposed relying on the theory of granulization to determine the caller's location. The expert, an FBI special agent, explained that to determine the location of a cell phone using [by] using the theory, [he] first identifies (1) the physical location of the cell sites used by the phone during the relevant time period; (2) the specific antenna used at each cell site; and (3) the direction of the antenna's coverage. He then estimates the range of each antenna's coverage based on the proximity of the tower to other towers in the area. This is the area in which the cell phone could connect with the tower given the angle of the antenna and the strength of the signal. Finally, [he] predicts where the coverage area of one tower will overlap with the coverage area of another.[fn104] The court excluded the testimony for the stated reasons that the theory had not been tested and had received no scrutiny outside the law enforcement community. [FN105] Whether the theory or technique has been subjected to peer review The peer review and publication prong of the Daubert factors was intended to increase the likelihood that flaws in methodology will be detected.[fn106] If a theory has been subjected to peer review, other experts have presumably had an opportunity to examine the author's reasoning and discover any methodological flaws in the reasoning. The first article in this series noted the voluminous literature on GPS technology. In the case of cell identification, however, many courts have looked to the wrong science. The theories behind radio waves have been subjected to peer review. However, as previously stated, the cell identification technique rests on additional assumptions. Courts should look to the technology, software, and equipment that a cellular carriers use to operate their networks. The problem is that some of this information is proprietary for competitive business purposes and the cell phone companies treat the information as trade secrets.[fn107] Companies do not want rival companies to steal their techniques and are fiercely protective of those that give them a competitive advantage in the market.[fn108] In United States v. Benford, the prosecution offered as an expert witness a radio frequency engineer employed by the cellular company used by the accused.[fn109] The engineer testified that his job was to assist with the management of the company's network and that he generated a map of the cell sites associated with each of the accused's cell phone calls on the date in question.[fn110] He then added circles to the map representing the approximate locations where the accused's phone was used. He testified that in order to connect to the cell site, the defendant's phone must have been within the cell site's coverage area.[fn111] The defense objected on the ground that the methodology of the proponent's expert had not been subjected to peer review.[fn112] The court dismissed the defense's concern by downplaying the significance of the peer review factors; the court

12 49 NO 3 CRIMLAWBULL ART 8 Page 12 asserted that peer review is only one of several factors to consider under Daubert.[FN113] In sustaining the admission of the testimony, the court in effect reverted to the old general acceptance standard.[fn114] Whether the technique has a known or potential known rate of error This prong of the Daubert analysis is intended to encourage the proponent of expert testimony to establish the known error rates for the expert's technique. When the proponent does so, the trier of fact is in a much better position to decide how much weight, if any, to ascribe to the expert testimony.[fn115] The prior article in this series pointed out that the government has released more than 70 studies of the error rate and margin in GPS technology. The difficulty with the cell identification technique is that as in the case of the second Daubert factor, the cell phone companies have tended to withhold this information from the public. Data about potential rates of error regarding the assignment of a cell phone to a particular cell site are not generally publicly available, and the companies tend to treat the data as proprietary information. Just as a cellular company does not want to share its processes and techniques with potential competitors, the typical company may not want to tell its customers how often its network does not operate correctly. In Benford, the defense also objected to the expert's testimony on the ground that the error rates of his methodology were unknown. As in the case of the peer review factor, the court summarily dismissed the defense's concern about known rates of error, remarking that the error rate factor is merely one of many non dispositive factors to consider.[fn116] Likewise, the court in United States v. Schaffer[FN117] essentially sidestepped the importance of known rates of error. The court went so far as to state that because the technique had been used by the particular witness without error, on at least 100 occasions, the technique had clearly proven reliable.[fn118] As a practical matter, it was left to the defense to unearth and introduce evidence indicating rates of error to attack the weight of the proponent's evidence. Needless to say, if the cell phone companies will not voluntarily disclose that information to the prosecution, they are likely to resist defense attempts to discover and disclose the information. In truth, in both Benford and Schaffer the proponent's expert's methodology consisted of nothing more than plotting data from the call detail records onto a map. The witnesses' testimony did not detail the methodology by which the cell company's network assigns a cell phone to a particular cell site or describe the error rates of the methodology. Whether there are standards for controlling the technique's operation The Daubert Court identified the existence and maintenance of standards controlling the technique's operation as indicative of the technique's trustworthiness.[fn119] In the case of GPS evidence, there are published governmental standards for maintaining and operating the system. The problem with cell identification and the related use of call record data is that each carrier has developed its own internal standards to monitor and maintain their equipment; there are no universal standards governing the functioning of cell sites, which is crucial to understanding the significance of a cell phone's connection with any given cell site. As in the case of the peer review and error rate factor, courts often give this consideration short shrift in the cell tower cases. As previously stated, in one such case the Court of Appeals for the Fifth Circuit fell back on the general acceptance factor to justify the admission of the proponent's expert testimony. In Benford, the court skipped over this factor altogether when it stated that Daubert addressed only four general criteria. [FN120] The court in Allums did the essentially same thing.[fn121]

13 49 NO 3 CRIMLAWBULL ART 8 Page 13 Whether the theory or technique has gained general acceptance[fn122] Courts often assert that cell tower evidence i.e., the cell identification technique is generally accepted. However, that assertion is conclusory. The technique has repeatedly been deemed generally accepted with little questioning. Courts often call the technique generally accepted simply because investigators have employed the technique in the past and courts have allowed them to do so. For example, in Allums, the court's entire analysis of the general acceptance factor was the following passage: The methodology has been utilized in hundreds of prior investigations, allowing the FBI to use cell tower data to successfully track and apprehend fugitive. The methodology has therefore been tested, and has general acceptance in the area of law enforcement. [FN123] In that passage, the Allums court commits two errors. First, without citing any empirical support, the court simply states that the technique has been successfully employed in the past. It is undeniable that the technique has been employed in the past, but, without any data as to error rate, it is fallacious to assume that the prior uses of the technique have uniformly led to correct findings. Secondly, the court assumes that the relevant area of expertise is law enforcement. Frye and Daubert refer to the acceptance of the technique by the relevant scientific communities. Even if law enforcement is a pertinent community, there are certainly more relevant scientific fields and the court did not insist on an identification of those fields or a showing of acceptance in those fields. It is certainly dubious to claim that the relevant scientific communities generally accept the proposition that by using the cell identification technique, an expert can accurately determine a caller's precise location. For their part, Manfred Schenk and several other engineers have testified in no uncertain terms that at most the technique can place the caller in a more or less large geographical coverage range sometimes ranging up to 452 miles. The upshot of a rigorous Daubert analysis is the conclusion that trial judges should not permit experts relying on the cell identification technique to opine about a caller's position at the time of a call.[fn124] Given the available empirical data, the judge should allow the expert to testify only that the caller was somewhere within an estimated coverage area.[fn125] It would be an entirely different matter if the expert marshaled enough to apply an alternative technique such as AOA, TOA, or TDOA. Given sufficient facts, an expert using one of those techniques can reasonably estimate a caller's location at the time of the call. However, as Part III pointed out, in the real world experts can almost never resort to those techniques because, as a result of quite sensible business decisions, cell phone companies have chosen not to collect the data needed to use those alternative techniques. V. CONCLUSION The first article in this series demonstrated that GPS technology can enable an expert to accurately determine the location of a receiver. As we have seen in this article, there are also cell phones techniques for locating a caller's location with a fair degree of accuracy. The TOA and TDOA techniques can locate a user from within 50 to 150 meters. Even the less accurate AOA technique can place a user within about 100 to 200 meters. The rub is that these techniques rely on angulation and lateration. The cell phone company's normal call data records do not include the types of information needed to perform the angulation and lateration calculations. By default, in the typical case the cell identification method is the only technique available to create a historical record of a suspect's location. At best, the use of that technique enables an expert place a suspect's cell phone within a geographical zone that varies in size depending on a number of factors.[fn126] In rural areas the area can be as large as 452 square miles. Even in urban areas with more cell sites and smaller coverage areas, the zone can still only place an individual within 5-6 square miles.[fn127]

14 49 NO 3 CRIMLAWBULL ART 8 Page 14 In the past, the courts have accepted cell identification as a valid technique for determining a caller's location. However, the review in the Daubert factors in Part IV of this article suggests that courts should be more skeptical of the claims of experts relying on the cell identification technique. Some courts have implicitly and mistakenly treated the general scientific principles of radio waves as a sufficient basis for the cell identification technique. Instead, courts should focus on the specific methods that cell companies apply in their networks to utilize the general scientific principles of radio waves to facilitate cellular communications. The reliability of the technique depends on the equipment and algorithms used by the individual cell provider company. Because the companies' information is proprietary, the information has not been peer reviewed, known error rates are not publicly available, and there are no universal standards. Further, in assessing the acceptance of these techniques, courts should not treat law enforcement as the only relevant community. Courts ought to broaden the analysis to weigh the views of radio frequency engineers or other scientists capable of evaluating the properties and functions of a cellular network. Unfortunately, courts have been lax in performing their gatekeeper function in the cell tower evidence cases. At this time, courts admit the proponent's evidence with little scrutiny. As a result, the opponents' only meaningful recourse is to attack the weight of the proponent's evidence by calling their own expert witness to convince the trier of fact that the cell identification technique does not warrant the inference drawn by the proponent's expert. Hopefully, in time, courts will gain a more sophisticated understanding of the operation of cellular networks and begin to flex their gatekeeper muscles more aggressively. [FN*] James Beck: J.D., 2012, University of California Davis School of Law, Law Clerk, the Honorable Johnnie B. Rawlinson, United States Court of Appeals for the Ninth Circuit, Las Vegas, Nevada. Christopher Magana: J.D., 2012, University of California Davis School of Law, Associate, Morrison & Forester, San Francisco, California. Edward J. Imwinkelried: Professor of Law, University of California Davis; coauthor, Paul C. Giannelli, Edward J. Imwinkelried, Andrea Roth & Jane Campbell Moriarity, Scientific Evidence (5th ed. 2012). These two articles are based largely on the seminar papers that Messrs. Beck and Magana submitted in Professor Imwinkelried's Spring 2012 Scientific Evidence seminar at the University of California, Davis School of Law. [FN1] See Fed. Commc'n Comm'n, PS Docket No , Wireless 911 Accuracy Requirements (2011). The FCC requires cell phone companies to be able to locate a 911 caller using network-based techniques within 100 meters 67% of the time and within 300 meters 90% of the time. The handset-based requirements are much stricter, requiring location accuracy within 50 meters 67% of the time and within 150 meters 90% of the time. [FN2] The use of cell tower evidence obviously raises other issues such as Fourth Amendment questions. U.S. v. Graham, 846 F. Supp. 2d 384 (D. Md. 2012); Mike Carcella, Cops + Data = Cell Division: Judges Weigh the Legality of Law Enforcement's Use of Mobile-Phone Data, Nat'l L.J., Aug. 27, 2012, at 1. [FN3] It is also possible to use real-time cell site data. The data is gathered as a cell phone constantly scans the cellular network for the site with the strongest signal. Aaron Blank, The Limitations and Ad-

15 49 NO 3 CRIMLAWBULL ART 8 Page 15 missibility of Using Historical Cellular Site Data to Track the Location of a Cellular Phone, 18 Rich. J.L. & Tech. 3, 10 (2011) [hereinafter Blank]. However, the focus of this article is on the more [common fact situation in which the police must rely on historical cell site data records. [FN4] Michael Cherry et al., Cell Tower Junk Science, 95 Judicature 151, 151 (2012) [hereinafter Cherry]. [FN5] Guy Clemens, The Cellphone: The History and Technology of the Gadget that Changed the World (2010) [hereinafter Clemens]. [FN6] Clemens, supra note 5, at [FN7] Clemens, supra note 5, at [FN8] Clemens, supra note 5, at [FN9] Thomas Farley & Ken Schmidt, Cellular Telephone Basics, Cell and Sector Terminology, Privateline: Telecommunications Expertise (Jan. 1, 2006), [hereinafter Farley]. [FN10] Farley, supra note 9. [FN11] Terrence P. O'Connor, Provider Side Cell Phone Forensics, 3 Small Scale Digital Device Forensics J. 1, 3 (2009) [hereinafter O'Connor]. [FN12] In re Application of U.S. for an Order for Prospective Cell Site Location Information on a Certain Cellular Telephone, 460 F. Supp. 2d 448, 450 (S.D. N.Y. 2006). [FN13] O'Connor, supra note 11 at 3. [FN14] In re Application of U.S. for an Order for Prospective Cell Site Location Information on a Certain Cellular Telephone, 460 F. Supp. 2d 448 (S.D. N.Y. 2006). [FN15] Farley, supra note 9. [FN16] Thomas Farley & Ken Schmidt, Cellular Telephone Basics, Registration Hello World!, Privateline: Telecommunications Expertise (Jan. 1, 2006), [FN17] See Wayne Jansen & Rick Ayers, Nat'l Inst. of Standards & Tech., Guidelines on Cell Phone Forensics: Recommendations of the National Institute of Standards and Technology 40 (2007) [hereinafter Jansen]. [FN18] See 18 U.S.C.A (2002). [FN19] Thomas Farley & Ken Schmidt, Cellular Telephone Basics, Registration Hello World!, Privateline: Telecommunications Expertise (Jan. 1, 2006),

16 49 NO 3 CRIMLAWBULL ART 8 Page 16 [FN20] Jansen, supra note 17, at 34. [FN21] Jansen, supra note 17, at 61. [FN22] Jansen, supra note 17, at 63. [FN23] See O'Connor, supra note 11, at 1. [FN24] See Jansen, supra note 17, at 61. [FN25] Jansen, supra note 17, at 51. [FN26] Cell Phone Location Tracking Request Response Cell Phone Company Data Retention Chart, ACLU (April 24, 2012), art. [FN27] Jansen, supra note 17, at 63. [FN28] Cherry, supra note 4, at 151. [FN29] Cherry, supra note 4, at 151. [FN30] SIM cards are portable integrated circuits installed in cell phones that aid in the authentication of the cell phone to the network. They also store phone contacts and other data, in particular they store the raw measurements of radio signals between a phone and the cell sites with which it communicates. [FN31] Jagdish Rebello, Four Out of Five Cell Phones Integrate GPS by End of 2011, isupply (July 16, 2010), s-to-integrate-gps-by-end-of-2011.aspx. [FN32] See Cisco, Wi-Fi Location-Based Services 4.1 Guide 2-2 (2008) [hereinafter Cisco]. [FN33] See Shu Wang et al., Location Based Services for Mobiles: Technologies and Standards 74 (2008) [hereinafter Shu Wang]. [FN34] See Cisco, supra note 32, at 2-2. [FN35] See O'Connor, supra note 11, at 3. [FN36] See O'Connor, supra note 11, at 3. [FN37] Twelve miles is considered to be the maximum range for a mobile phone to its receiving antenna. See O'Connor, supra note 11, at 3. [FN38] Area of a circle equals r 2. Therefore, the coverage area of a tower with a radius of 12 miles is square miles ( 12 2 = ). [FN39] See O'Connor, supra note 11, at 3.

17 49 NO 3 CRIMLAWBULL ART 8 Page 17 [FN40] Each antenna is designed to cover 120 but there is overlap of 20 on each side with the other antennas such that each antenna covers about 160. See O'Connor, supra note 11, at 3. [FN41] 12 2 (160/360)= [FN42] See Cisco, supra note 32, at 2-2. [FN43] Cisco, supra note 32, at 2-2; Aaron Blank, The Limitations and Admissibility of Using Historical Cellular Site Data to Track the Location of a Cellular Phone, 18 Rich. J. Law & Tech. 1, 12 (2011). [FN44] See Cisco, supra note 32, at 2-2. [FN45] Cisco, supra note 32, at 2-9. [FN46] Cisco, supra note 32, at 2-9. [FN47] Cisco, supra note 32, at [FN48] Cisco, supra note 32, at [FN49] Cisco, supra note 32, at 2-10 to [FN50] See Shu Wang, supra note 33, at 74. [FN51] See Cisco, supra note 32, at [FN52] Cisco, supra note 32, at 2-3. [FN53] Cisco, supra note 32, at 2-3, 2-4. [FN54] Cisco, supra note 32, at 2-3, 2-4. [FN55] Cisco, supra note 32, at 2-3, 2-4. [FN56] Cisco, supra note 32, at 2-3, 2-4. [FN57] Cisco, supra note 32, at 2-3, 2-4. [FN58] Martyn Malick, Mobile Positioning Techniques 409 (2003). [FN59] See Cisco, supra note 32, at 2-4. [FN60] Cisco, supra note 32, at 2-5. [FN61] Cisco, supra note 32, at 2-5. [FN62] Cisco, supra note 32, at 2-5. [FN63] Cisco, supra note 32, at 2-5. [FN64] See Shu Wang, supra note 33, at 74.

18 49 NO 3 CRIMLAWBULL ART 8 Page 18 [FN65] See Cisco, supra note 32, at 2-5. [FN66] Cisco, supra note 32, at 2-5. [FN67] Cisco, supra note 32, at 2-5. [FN68] Cisco, supra note 32, at 2-5, 2-6. [FN69] Cisco, supra note 32, at 2-5. [FN70] Cisco, supra note 32, at 2-6. [FN71] Martin Dolan et al., Improving Your Criminal Practice: Use of Cell Phone Records and GPS Tracking, 24 CBA Record 38, 38 (2010) [hereinafter Dolan]. [FN72] Amy Lai, Dangerous Proximity: Using High-Tech Evidence in the Criminal Prosecution of Domestic Violence, 48 Crim. L. Bull. 537, 548 (2012) [hereinafter Lai]; People v. Wilkins, 56 Cal. 4th 333, 153 Cal. Rptr. 3d 519, 295 P.3d 903 (2013). [FN73] Dolan, supra note 71, at 39. [FN74] Jansen, supra note 17, app. D (the article lists the types of data that cell phone data records are required to store; angle of arrival and distance to more than one cell tower are not included); Blank, supra note 3, at 13 ( [N]o business purpose exists for recording real-time cell site data, and cellular companies tend to only keep records of historical cell site data that are useful for billing purposes or to measure call traffic. [C]ompanies may only store data for six to twelve months before purging it from a cellular company's system. ). [FN75] See Declan McCullagh, Feds Push or Tracking Cell Phones, CNET News (Feb. 11, 2010) (noting that network providers generally have no business reason to store moment-by-moment logs of when each mobile unit contacts a tower). [FN76] Fed. R. Evid [FN77] Fed. R. Evid [FN78] We confess that this pun is intended. [FN79] See, e.g., U.S. v. Benford, 2010 WL (N.D. Ind. 2010); U.S. v. Allums, 2009 WL (D. Utah 2009); U.S. v. Mendoza-Morales, 2007 WL (D. Or. 2007). See also Lai, supra note 72, at (it is a mistake to think that this technique is a fairly exact science ). [FN80] See, e.g., U.S. v. Benford, 2010 WL (N.D. Ind. 2010); U.S. v. Allums, 2009 WL (D. Utah 2009); U.S. v. Mendoza-Morales, 2007 WL (D. Or. 2007). [FN81] See, e.g., Wilson v. State, 195 S.W.3d 193, (Tex. App. San Antonio 2006). [FN82] Blank, supra note 3, at 25 27, citing Perez v. State, 980 So. 2d 1126, (Fla. 3d DCA 2008), and State v. Hayes, 2010 WL (Tenn. Crim. App. 2010), appeal denied, (May 25, 2011).

19 49 NO 3 CRIMLAWBULL ART 8 Page 19 [FN83] Blank, supra note 3, at 25 26, citing Perez v. State, 980 So. 2d 1126, (Fla. 3d DCA 2008). [FN84] Wilson, 195 S.W.3d at [FN85] Wilson, 195 S.W.3d at [FN86] Wilson, 195 S.W.3d at [FN87] Blank, supra note 3, at 3-36, citing Wilder v. State, 191 Md. App. 319, 991 A.2d 172 (2010), and U.S. v. Yeley-Davis, 632 F.3d 673, 84 Fed. R. Evid. Serv. 723 (10th Cir. 2011), cert. denied, 131 S. Ct. 2172, 179 L. Ed. 2d 951 (2011); U.S. v. Evans, 892 F. Supp. 2d 949 (N.D. Ill. 2012) ( the court respectfully disagrees with those courts that have allowed law enforcement officers to provide lay opinion testimony as to how cellular networks operate or the use of call data records to determine the location of a cell phone ); Payne v. State, 2013 WL (Md. Ct. Spec. App. 2013). [FN88] Blank, supra note 3, at ( Three types of experts may testify regarding cell site location evidence: law enforcement; agents from cellular companies; and a hybrid approach featuring some combination of the two. ). [FN89] Blank, supra note 3, at 38 ( Among law enforcement, a wide spectrum of background and experience have been found sufficient to qualify an expert. ). [FN90] See Saenz v. State, 2011 WL (Tex. App. Corpus Christi 2011), petition for discretionary review refused, (June 8, 2011). See also Amy Lai, supra note 72, at 549 ( law enforcement officers with minimal training ). [FN91] See Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, , 113 S. Ct. 2786, 125 L. Ed. 2d 469, 27 U.S.P.Q.2d 1200, Prod. Liab. Rep. (CCH) P 13494, 37 Fed. R. Evid. Serv. 1, 23 Envtl. L. Rep (1993); U.S. v. Evans, 892 F. Supp. 2d 949 (N.D. Ill. 2012); Blank, supra note 3, at 42. [FN92] Fed. R. Evid See also Miguel Méndez, Evidence A Concise Comparison of the Federal Rules with the California Code 7.03 (2010). [FN93] Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 589, 113 S. Ct. 2786, 125 L. Ed. 2d 469, 27 U.S.P.Q.2d 1200, Prod. Liab. Rep. (CCH) P 13494, 37 Fed. R. Evid. Serv. 1, 23 Envtl. L. Rep (1993)). [FN94] Daubert, 509 U.S. at 593. [FN95] See Paul C. Giannelli, Edward J. Imwinkelried, Andrea Roth & Jane Campbell Moriarity, Scientific Evidence 1.08 (5th ed. 2012) [hereinafter Giannelli]. [FN96] General Elec. Co. v. Joiner, 522 U.S. 136, 146, 118 S. Ct. 512, 139 L. Ed. 2d 508, 18 O.S.H. Cas. (BNA) 1097, Prod. Liab. Rep. (CCH) P 15120, 48 Fed. R. Evid. Serv. 1, 28 Envtl. L. Rep , 177 A.L.R. Fed. 667 (1997).

20 49 NO 3 CRIMLAWBULL ART 8 Page 20 [FN97] Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 147, 119 S. Ct. 1167, 143 L. Ed. 2d 238, 50 U.S.P.Q.2d 1177, Prod. Liab. Rep. (CCH) P 15470, 50 Fed. R. Evid. Serv. 1373, 29 Envtl. L. Rep (1999). [FN98] D. Michael Risinger, Defining the Task at Hand : Non-Science Forensic Science After Kumho Tire Co. v. Carmichael, 57 Wash. & Lee L. Rev. 767 (2000); Edward J. Imwinkelried, The Meaning of Appropriate Validation in Daubert Interpreted in Light of the Broader Rationalist Tradition, Not the Narrow Scientific Tradition, 30 Fla. St. U. L. Rev. 735, (2003). [FN99] Blank, supra note 3, at 16, 34 35; U.S. v. Evans, 892 F. Supp. 2d 949 (N.D. Ill. 2012) ( the testimony concerning how cellular networks [generally] operate would be helpful because it would allow the jury to narrow the possible locations of Evans' phone during the course of the conspiracy ). [FN100] Blank, supra note 3, at 16. [FN101] Testimony of Mr. Manfred Schenk in People v. Williams, No FC, slip op. at 4 (Mich. Cir. Ct., Mar. 6, 2012). [FN102] People v. Williams, No FC, slip op. at 4. [FN103] U.S. v. Evans, 892 F. Supp. 2d 949 (N.D. Ill. 2012). [FN104] U.S. v. Evans, 892 F. Supp. 2d 949 (N.D. Ill. 2012). [FN105] U.S. v. Evans, 892 F. Supp. 2d 949 (N.D. Ill. 2012). [FN106] See Giannelli, supra note 95, 1.08[b], at [FN107] Telephone interview with Mr. Michael Cherry, CEO, Cherrybiometrics (Apr. 11, 2012). [FN108] Telephonic interview with Mr. Michael Cherry, CEO, Cherrybiometrics (Apr. 11, 2012). [FN109] U.S. v. Benford, 2010 WL (N.D. Ind. 2010). [FN110] U.S. v. Benford, 2010 WL (N.D. Ind. 2010). [FN111] U.S. v. Benford, 2010 WL (N.D. Ind. 2010). [FN112] U.S. v. Benford, 2010 WL (N.D. Ind. 2010). [FN113] U.S. v. Benford, 2010 WL (N.D. Ind. 2010). [FN114] U.S. v. Benford, 2010 WL (N.D. Ind. 2010) ( Imrisek testified that there is no dispute in his technical community as to the methods he use. [His] reliance on the [call data records] served as a reliable basis for his testimony because these materials are facts or data of a type reasonably relied upon by experts in the field of cell phone and cell tower technology. ). Under Frye v. U.S., 293 F. 1013, 34 A.L.R. 145 (App. D.C. 1923), scientific testimony was admissible if it rested on a technique or theory that was generally accepted in a given field.