Introduction to Crime Scene Dynamics

Transcription

1 Chapter 1 Introduction to Crime Scene Dynamics OVERVIEW The development of the field of forensics has been a process steeped in science and research. On the other hand, the practice of crime scene investigation and the crucial role of the first officer on the scene has developed sporadically. The premise of crime scene investigation is clear: do not touch or disturb anything that could destroy or contaminate evidence. However, it has been a lesson fraught with costly mistakes resulting in the loss of invaluable evidence and claims of police ineptitude or corruption. The merger of the two areas: forensics, or more accurately, criminalistics and crime scene investigation, has only recently become a team effort. CHAPTER OBJECTIVES 1. Discuss the overview of forensics, criminalistics, and crime scene management 2. Identify the various fields of study in forensics 3. Explain the interdisciplinary nature of forensics 1

2 2 Introduction to Crime Scene Dynamics Chapter 1 Officer training and the development of permanent, civilian crime scene specialists have dramatically changed the dynamics of crime scene investigation. Crime scene investigation has evolved from a continuing in-service training ground for officers to a specialized position requiring expertise and savvy field knowledge. While this book includes practical information on crime scenes and the handling of evidence, it is not meant to replace or dismiss professional training courses or texts on either subject, but rather as a broad overview, with some resources and information that may be of use to the reader. The purpose of this text is to whet the reader s appetite for the subject and spark an interest so the reader will continue to study the subject and eventually gain practical experience in the field. THE BROAD VIEW OF FORENSICS AND CRIME SCENE DYNAMICS Today crime scene dynamics are a blend of investigative experience, science, psychology, and technology that have enabled law enforcement to solve many crimes that once would have been considered unsolvable. During the past few decades, the science of forensics has grow exponentially. The development of such techniques as automated and integrated fingerprint comparisons, databases, DNA genetic markers, forensic anthropology, odontology, entymology, serology, taphony, (study of bones) ballistics, and many more fields has revolutionized forensics. Forensics itself has been transformed from a variety of disjointed areas of scientific or medio-legal emphasis to a highly sophisticated combination of resources to be used in the war on crime. The ultimate goal is the successful apprehension and prosecution of the perpetrator. One of the unexpected benefits of the evolution of forensics is the exclusion of a suspect based on exculpatory evidence. Exculpatory evidence is evidence that clears an individual from fault or guilt. Exculpatory evidence can be used to clear an individual convicted based on faulty investigation or convicted before the advent of DNA analysis. The Innocent Project, a non-profit legal clinic founded by Barry C. Scheck and Peter J. Neufeld at the Benjamin N. Cardozo School of Law in 1992, has cleared 138 individuals through post-conviction DNA testing as of December Their sole purpose is to review cases where

3 Chapter 1 Introduction to Crime Scene Dynamics 3 post conviction DNA testing of evidence may yield conclusive proof of innocence. 1 FORENSIC SPECIALISTS VS. CRIMINALISTS There are four layers of roles and responsibilities in a crime scene investigation. The first layer consists of the first person assigned to the call or the first person on the scene, usually a law enforcement official or emergency response personnel. The second layer is a forensic crime scene specialist or evidence technician. A forensic specialist or crime scene technician is usually a field technician who responds to the crime scene and physically collects and transports evidence. Technicians may conduct some presumptive tests or some tests in the lab, but their role differs from that of criminalists. Technician training is related to the collection and preservation of evidence, not the analysis of the evidence. In many departments, particularly smaller to medium sized departments, one or two people may be generalists who handle a combination of tasks such as searching for evidence, photographing the crime scene, collecting and transporting evidence, and lifting fingerprints or other types of evidence. The third layer consists of those who collect and analyze fingerprint evidence, latent print examiners. In most departments the individual who collects the physical evidence is also responsible for collecting fingerprint evidence from the scene. A latent print examiner or comparison expert analyzes the prints and tries to compare them with fingerprints stored in the automated fingerprint databases. The fourth and final layer is the criminalist, who specializes in analyzing the evidence brought into the crime lab. Criminalists are often scientists with a background in the hard sciences, for example chemistry or biology. In some cases they may be experts in a particular field, such

4 4 Introduction to Crime Scene Dynamics Chapter 1 as DNA, tool marks, firearms, or ballistics. Forensic science is derived not only from chemistry and biology but also from medicine, anatomy, and pathology. The California Association of Criminalists has a brief description of the variety of roles played by criminalist, which are described in the following sections. 2 FIREARMS AND TOOLMARKS Criminalists provide information to investigators about the caliber and type of firearm used in a crime. The barrel of a pistol or rifle leaves scratches or striation marks on bullets. Once a firearm is recovered, these marks can individualize a bullet to a unique firearm to the exclusion of all other firearms. Similarly, tools used in crimes can leave striation and other marks on surfaces. These marks can be compared to the tool believed to have made them. If the comparison is a positive match, a tool may be individualized as having made the mark to the exclusion of all other tools. A computer database of marks on cartridge cases and bullets has been developed to link a particular firearm to serial crimes.

5 Chapter 1 Introduction to Crime Scene Dynamics 5 TRACE EVIDENCE Trace evidence, frequently overlooked because of its microscopic size, applies micro analysis to fibers, hair, soil, paint, glass, pollen, explosives, gunshot residue, food, plastic bags, and virtually anything involved in a crime. No training exists to prepare the trace evidence analyst for every kind of case that will cross the workbench, as each case is fascinatingly unique. By having a thorough knowledge of the advantages and disadvantages of microscopic, spectroscopic, and chromatographic methods, the criminalist can meet the analytical challenge of each case. DNA AND SEROLOGY In the mid 1980s deoxyribonucleic acid (DNA) techniques began to be applied to forensic cases. Any tissue from the body carrying the genetic code of DNA can be used to compare to a standard. This allows blood to be linked uniquely to a single individual. Databases of DNA profiles are being compiled to aid in identifying criminals and have been used to solve old cases, where samples were properly preserved and reanalyzed. In some cases, innocent persons have been released from prison based on the reanalysis.

6 6 Introduction to Crime Scene Dynamics Chapter 1 DRUGS, ALCOHOL, AND TOXICOLOGY Criminalists use a battery of analytical tools and the knowledge of chemistry to identify controlled substances in powders, pills and liquids, and body fluids. Investigators may call criminalists to clandestine laboratories where illegal drugs are produced. Criminalists are frequently responsible for maintaining breath alcohol analysis instruments and training laboratory technicians and police officers who run the tests on individuals suspected of driving under the influence. Sometimes no controlled substances are present or in other cases several drugs maybe detected in a sample. SUMMARY Criminalistics is one of many divisions in the field of forensic science. Forensic science includes forensic pathology, odontology, entomology, engineering, criminology, and other disciplines. These are all specialized sections in forensic science. Criminalists use techniques learned in chemistry, molecular biology, geology, and other scientific disciplines to investigate and solve crimes. Criminalistics should not be confused with the field of criminology. Criminologists are sociologists, psychologists, and others who study the causes and effects of crime on society. For the criminalist, crime scene investigation involves the recognition, documentation, collection, preservation, and interpretation of physical evidence, which may be as big as a truck or as small as a diatom or pollen grain. Recognition of items out of place, articles improperly located, or items added to the crime scene are an important part of crime scene processing. The criminalist collects, preserves, and makes interpretations about the evidence and their relation to the series of events resulting at the crime scene. The criminalist brings evidence back to the laboratory where examinations are conducted.

7 Chapter 1 Introduction to Crime Scene Dynamics 7 Interpretations are made about the relevance of a particular item from the crime scene by associating particular items of evidence to specific sources and reconstructing the crime scene. This means not only associating a suspect with a scene but also the telling of a story about what transpired before, during, and after the crime. Criminalists draw on a wide spectrum of scientific knowledge including chemistry, biology, genetics, molecular biology, physics, statistics, and a working knowledge of civil and criminal law. Applying this knowledge, criminalists associate and identify evidence, interpret the results, reconstruct the crime scene, and write a report summarizing the findings. Finally, criminalists testify as expert witnesses, explaining to the judge and jury how their conclusions were reached in the crime lab. Depending upon one s interests, skills, and abilities there are virtually no limits to the depth and breadth of the field of forensics. Most career decisions come down to a preference for either working in the field or in the crime lab. While many criminalists respond to the field to examine cases, they are more likely to be found in the crime lab. DISCUSSION QUESTIONS 1. What are the key differences between the position of criminalist and field evidence or forensic specialist? 2. What education or training is necessary to be a criminalist? 3. Define exculpatory evidence as it relates to forensics. ENDNOTES