Forensic Science Final Exam Review

Transcription

1 Forensic Science Final Exam Review Human Identity (Fingerprints, Forensic Anthropology, DNA) 1.Who developed the system known as anthropometry? Bertillion 2.Who postulated the exchange of evidence principle? Locard 3.In comparing footwear samples, you look for both class and individualizing characteristics. Give examples of each. Class: tread pattern, shoe size, logo Ind: gauge/hole in sole, wear pattern 4.What are 4 factors that can be rightfully cited as an explanation for the rapid growth of crime labs during the last 25 years? Increase in crime rate Supreme Court decisions during the 1960 s that resulted in fewer confessions Increased drug use Advent of DNA profiling 5. Which unit has the responsibility for the examination of body fluids and organs for the presence of drugs and poisons? the toxicology unit 6.The final evaluator of forensic evidence is the jury. 7.The first rule in crime scene photography is: do not touch/move/disturb evidence unless it is in imminent danger of being lost/destroyed 8.What factors help an investigator decide how to search a crime scene? Size of scene, locale, type of crime, available search team, scope of scene 9. Any object that can establish that a crime has been committed or can link a crime and its victim or perpetrator is called physical evidence. 10.Whose responsibility is it to secure the crime scene? The first responding officer 11.Why must notes be taken during the documentation of a crime scene? the investigator may be called upon months or years later to testify and cannot rely on his or her memory alone to recall details of the scene. 12.Hair samples, blood samples, bullets, hand swabs, etc, are all evidence that would logically found or taken at what kinds of crime scenes? Violent crime 13.List some techniques scientists use in order to be able to visualize latent fingerprints: oblique lighting, alternate light source, special powders, chemical reagents, superglue fuming 14. Which skeletal features are most useful in estimating skeletal age? Skull (teeth, sutures) and other places on the skeleton where growth plates (epiphyses) fuse as the person ages 15.The skull and the pelvis are the most sexually dimorphic features of the human skeleton.

2 16.The analysis of skeletal remains within a legal investigation is called forensic anthropology. 17. How do male and female skeletons compare prior to puberty? They are virtually identical Which features about the human skeleton allow us to determine gender? Skull and pelvis are most helpful, but male skeleton is more robust while the female is more gracile Age? Sutures, dentition, growth plates Stature length of long bones and analysis with regression formulas 18.What is The Body Farm? a research facility where human remains are studied as they decay in order to gain a better understanding of decay processes and timelines 19.The cooling of the body after death is referred to as algor mortis. 20. Loops, whorls, and arches are considered to be which type of characteristic? (Class, individual, etc) 21.Under which circumstances have two people been found to have identical fingerprints? None to date 22. What is AFIS? Database for fingerprints What is CODIS? Database for DNA 23. From whom, and in what proportions, do you inherit your DNA? Half from each parent 24. Why is DNA considered to be the gold standard of identification? it is statistically unique and is scientifically analyzed (there is not subjectivity about it) 25. Under what circumstances might two people have identical DNA? Identical twins 26. How is DNA analyzed (2 lab techniques that we discussed)? Traditional gel electrophoresis and capillary gel electrophoresis 27. How is the identification of a victim, suspect, etc. different in reality from what is portrayed in TV crime series? Not everyone is in CODIS or AFIS and the time that it takes to identify someone/solve a crime is much longer than what is usually portrayed on television 28. What does a forensic odontologist study? Teeth What kinds of evidence might s(he) analyze? Dental records, skeletal remains of the jaw and teeth, bite marks 29. Are crime labs infallible? No- in fact, some have been found to have corrupt individuals who have tainted the cases on which they worked. Trace Evidence Analysis and Identification 30. In general, hairs and fibers are difficult to individualize. Because of this, they are considered to have mainly class characteristics. 31. The central region of a hair may contain a structure called the medulla, which may be continuous, interrupted, or fragmented. 32.The follicle tag is the part of the hair that is most likely to contain DNA.

3 33.If DNA is found from hair and is matched to a known DNA sample, then the hair is considered to have individualizing characteristics. 34.One difference between human and animal hair is the frequent absence of the medulla in humans. 35.The outer layer of a hair is the cuticle and it is covered in scales made of keratin. 36.The natural color of a strand of hair is determined by the number and concentration of pigment granules which are made of forms of melanin. 37.Synthetic fibers are made of large molecules called polymers which are made of smaller repeating units called monomers. These fibers are mass produced. Why is that a problem for forensic scientists? It increases the number of potential sources of fiber evidence 38.Give 4 examples of natural fibers. Cotton, silk, flax, hemp, asbestos What is the most common one? cotton 39.The first 2 characteristics that a fiber expert will compare in synthetic fiber sample are cross sectional shape and cross sectional diameter 40.One characteristic of a fiber can be that it might have two different indices of refraction. The difference between these indices is called birefringence 41. List (in order) the three stages of hair growth. Anagen, catagen, telogen 42.This hair growth stage is characterized by rapid cellular division in the root: anagen 43. Paint evidence is often analyzed by crime labs. What value can it have? Often transferred to tools or automobiles during crimes- can be used to associate two objects What tools do experts use to analyze and compare paint samples? Microscopes, pyrolysis gas chromatography 44. Soil (and other related material) is best examined by a forensic geologist 45. Soil can be useful evidence because: it can be carried into and out of crime scenes and can be narrowed down to particular source areas. Also, it may contain contaminants or peculiar materials specific to a certain location. Soil in a tire well can indicate where, and in which order, a car has travelled. 46. What role did trace evidence play in the McDonald murder case? There were synthetic fibers that were in question in an appeal and they were found to be consistent with the victim s wig. 47. What famous case involved the analysis of trace metals? The Kennedy Assassination Tools of the Forensic Scientist 48.What is one effect of the fact that light is a form of electromagnetic radiation? It can move through a vacuum (like space)- does not require a medium (material) in order to travel.

4 49. What is the mathematical relationship between the frequency, wavelength, and speed of light? c=λf 50. As wavelength increases, which color end of the visible spectrum is approached (blue or red)? 51. What is refraction? When the path of light is bent as the light moves from one material to another 52.In two of your labs, you used a device called a colorimeter. This instrument could be set at different wavelengths and was able to measure the absorbance of light by a solution. (our colorimeter uses the visible spectrum) 53. The general relationship between absorbance and concentration is known as Beer s law, and is what kind of mathematical relationship? Direct (as concentration increases, absorbance also increases) 54. How would the relationship in #53 look in a graph? Linear 55. How could we use the colorimeter in a forensics lab? (What applications could it have?) toxicology (determining concentration of poison/drug in a sample) analysis of pigment-containing substances (like ink from a ransom note or bad check) 56. What is the name for the little containers that we used in the colorimeter? cuvettes 57. What does each of the following do: gas chromatograph, mass spectrometer, FTIR, thin layer chromatography? For each test, indicate whether the results are definitive or presumptive. GC: separates mixtures into constituent parts using a carrier gas; high speed and reliable, but presumptive results MS: analyzes substance (or parts of a substance) based on the behavior of ionized particles as they move through a magnetic field; the results are definitive FTIR: analyzes substances based on their infrared fingerprint ; definitive results TLC: inexpensive, easy, fast- separates mixtures into component parts; Rf values can be compared to known substances; presumptive results 58. How is gas chromatography used in tandem with mass spectrometry? The parts that are separated via GC are sent directly to MS 59. What is an analyte in a chemical testing situation? The material being analyzed 60. Differentiate between the electron microscopes, comparison microscope, stereomicroscope, compound light microscope, and micro-spectrophotometer. (What is each good for? ) Electron microscopes (TEM, SEM): extremely high magnification potentials, high resolution; use electrons instead of visible light Comparison Microscope: side by side light microscopes connected by optical bridge; allows user to see magnified images side by side Stereomicroscope: upright, 3D image. Low magnifications but great for scanning large, bulky items for trace evidence. Compound light microscope: best general tool with variable magnification levels Micro-spectrophotometer: instrument that is attached to a compound light microscope and allows chemical analysis of materials as on observes them on a sample

5 Advanced Crime Scene Topics 61. What can investigators tell about a crime from bloodstains? (List at least 3 things) type of event (gunshot vs. stabbing, etc), manner in which the blood fell (drip, spurt from artery, project from object, etc), location in the space where the blood was produced, potential identification of victim/suspect, how many blows occurred (if blunt force trauma), where a missing object/person was with respect to the victim (if there is a void in the cast of or blow back spatter) 62. How does the shape of a blood stain change as the angle of impact increases (from zero to 90 degrees)? The closer to 90 degrees, the more circular the stain 63. Bloodstains that are created when the force acting on the blood is gravity are called passive 64. The smaller the size of the droplets in a spray of blood spatter, the: higher the velocity at which they were moving 65. How do experts determine the angle of impact of a bloodstain? 1. Measure length (not counting satellites or tails) and length of stain 2. Divide width by length 3. Take the inverse sine of the result 66. How do experts determine where in a space (such as a room) a blood spatter-producing event occurred? 1. back trace each stain to find the area(s) of convergence 2. measure the distance of each stain from the center of its area of convergence 3. determine the angle of impact 4. multiply the tangent of the impact angle by the distance 5. stains that have results within about a foot of one another probably came from the same event 67. How can an expert tell which way a blood drop was traveling before it hit a surface? The tail points in the direction it was travelling. 68. Be able to calculate angle of impact, find areas of convergence, etc. 69. How do investigators find blood evidence that is not visible to the naked eye? (More than one test) Luminol and Kastle Meyer 70. Are the test that you listed in #69 presumptive or confirmatory? Explain. Other materials (besides blood) can produce positive results with each of these. 71. What is PMI, and how are insects used to estimate it? Post Mortem Interval (time since death); flies lay eggs right away on a corpse and the larvae mature at specific rates depending on the species and the environmental temperature. 72. What factors affect the ability of adult flies to find a corpse and lay eggs on it? Flies usually won t fly in the rain (especially storms); if a body is tightly wrapped it will take them longer to find it and get to it. If a body is buried it will delay the flies. 73. The air temperature of the surroundings of a body is called the ambient temperature.

6 Firearms and ammunition identification 74. Any mark made in a softer surface by a harder implement is called a tool mark. 75. The purpose of the rifling in a barrel is to: make the bullet spin, which allows it to maintain its path. 74. The rifling lands leave deep marks in a bullet as it travels through the barrel, and the grooves leave raised areas on the bullet. Within these impressions are microscopic scratches called striations. These are unique to the firearm, so they are considered to have individualizing characteristics. Miscellaneous Diagrams 75. (Fingerprint pattern chart) Name of Pattern Incidence In US (most common/least common) Description of ridge lines Arch whorl Loop Least common Start at one side and leave on the other Enclose upon themselves in circular patterns Most common Start and leave on the same side Deltas (absent, one, Absent At least 2 1 two) Sub-types Plain and tented Double loop, pocket Ulnar and radial loop, accidental 76. Label the hair diagrams: 77. Be able to determine Rf values from a TLC plate (diagram) a- shaft b- root c- follicle d- cuticle e- e- medulla f- f- cortex 78. Be able to label the parts of a compound light microscope. 79. Be able to recognize a human hair vs an animal hair

7 80. Be able to recognize characteristics of female skeletal parts vs male 81. Be able to identify the following structures/features of a human skeleton (may not be the same diagrams, and you do need to know the major skull features that we learned- ie: occipital protuberance, nasal spine, zygomatic bone):