Science of Crime Scenes Introduction Science of Crime Scenes

The past is a mystery of necessity Humans love mysteries and discovery, whether it is about people, places, or things Past events cannot be experienced in the present, the past must be interpreted through: Documents Living participants Objects Some are intentional, others unintentional Science of Crime Scenes

Forensic science is a historical science A crime scene investigator (a CSI) or forensic scientist infers past criminal activity through the traces left by those involved (criminal and otherwise) Much like historians, archeologists, geologists, paleontologists, and others Science of Crime Scenes

Science of Crime Scenes Popular but with flaws Forensic science has always been popular but television and movies have made it much more so The popular focus on forensic science was quickly followed by interest in some of its problems Unethical employees Errors Wrongful convictions The patchwork jurisdictional nature of law and law enforcement, particularly in the United States, fragmented methods, approaches, and training Science of Crime Scenes

National Research Council Report, 2009 “Although research has been done in some disciplines, there is a notable dearth of peer-reviewed, published studies establishing the scientific bases and validity of many forensic methods” Science of Crime Scenes

What are the problems in forensic science? The complexity of nature and modern material culture The discipline’s focus on the individual The perception that forensic science is “only an applied science” The confounding effects of taphonomic processes Science of Crime Scenes

Problem 1: The complexity of nature and modern material culture Material culture refers to the physical aspects of a society, the objects made or modified by a human These objects surround a people and its activities and are defined by their properties When an object interacts with other objects or humans, it gains meaning and develops performance characteristics Science of Crime Scenes

Science of Crime Scenes Two Examples A baseball thrown through the window of a house A rock thrown through the window of a car Science of Crime Scenes

What must be understood In Event 1, the materials in play are quite different than in Event 2 Need to understand: what the objects are also the nature of their components the way those components were combined by natural or human actions the way they interacted. The interaction involves all the physics of the action (velocity, angle, rotation, surfaces, etc.) and the interaction (the rock, the window coating, the baseball, the plate glass) to produce the final results. Science of Crime Scenes

CSIs think in the abstract and the practical “Could a rock really have broken that auto window?” “Could this rock really have broken that auto window?” Consider all the possible combinations of interactions that occur all day long across the world and add to that those that involve alleged criminal activities. Not only do CSIs have to work with the world as it is but they also have to sort the criminal activity from everyday life Science of Crime Scenes

Problem 2: The Tyranny of the Particular Forensic science’s focus on individual, singular things creates additional complexities unknown to other sciences Other historical sciences work at different scales of observation Archaeology = social Geology = global Astronomy = universal An archaeologist would analyze all porcelain ceramics or porcelains from the St. James’ factory A forensic scientist would analyze this specific porcelain object as an object and its relation to a specific crime. Science of Crime Scenes

Most sciences don’t work to the particular Other sciences use deduction: From the specific (observations in an experiment, for example) to the general (development of principles or laws about phenomena in the world) But forensic science tends to use induction: From the general (all automotive paints, as an example) to the specific (the paint on the automobile in the current case Science of Crime Scenes

Avoid fallacies common to induction The fallacies of illicit transference The fallacy of composition: what is true of the parts is true of the whole If a red cotton fiber is found, the textile it came from need not be made only of red cotton The fallacy of division: what is true of the whole is true of it parts DNA from a person’s hair must match DNA from their blood (chimerism is when a person’s DNA sequence varies with tissue sampled) Science of Crime Scenes

Problem 3: A Book of Recipes Basic research leads to knowledge about the world, applied research leads to solutions to specific questions Forensic science is often classified as applied science because of its direct applicability to solving crime This takes a narrow and simplistic view of forensic science Forensic science studies a range of phenomena that no other science pays attention to in a way no other science does Forensic and crime scene science still has an uphill battle to fight to gain recognition as a “real” science Science of Crime Scenes

Problem 4: Entropy and Taphonomy Entropy: Loss of organization Taphonomy: Study of an organism from the time it dies These processes are at the heart of forensic science Few other sciences study them Not much literature or interest Science of Crime Scenes

Crime scenes are a process, not an event More than “bagging and tagging” If the crime scene is compromised, the entire case may be jeopardized Those who process crime scenes are—or should be—scientists with the requisite education and training appropriate for that kind of work Science of Crime Scenes

Systematic approach to crime scenes Protecting the scene(s) Documentation of the location, scene, and evidence Collection of the potential evidence Preservation of the evidence Labeling of evidence and related materials Chain-of-custody considerations Letter of transmittal (to the custodial agency or laboratory) Collection of reference materials (known samples for comparison) Science of Crime Scenes