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The Essence of Forensic Science
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  1. The Essence of Forensic Science An Introduction to Crime Scene Forensics Philosophy and Practice

  2. A Philosophy • The underlying premise of this course is that crime scene investigation is a scientific AND an investigative endeavor. • Success • Experience, • Creative thinking, • Logic • Correct application of the science and the scientific method. • Scene investigations are intensely intellectual exercises. To disagree is ignorance, inexperience or stupidity. As the legendary golf pro Bobby Jones is credited with saying about his profession • “Competitive golf is played mainly on a five-and-a-half-inch course... • the space between your ears.” • A competent crime scene investigation is as cerebral an exercise as any scientific endeavor in forensic science, including forensic DNA analysis. Scene investigations are comprehensive, tedious and difficult scientific exercises that dovetail investigations and experience.

  3. Terminology • Police officers and scientists who investigate crime scenes are variably called crime scene investigators, forensic investigators or technicians depending on the jurisdiction in which they work. • Crime Scene Technician • For the discussions in this text, the term “crime scene technician” is neither employed nor appropriate. The term is demeaning to the scientists and specialized investigators who do this work. • Scene investigator: • A police officer/detective or other non-scientist working a scene. • Scene scientist: • A scientist working at the scene is a scene scientist. May or may not be a scene investigator. For these lectures, individuals who investigate crime scenes are considered collectively as scene scientists/investigators.

  4. A Common Perception • Lawyers, law enforcement officials, politicians, and even forensic scientists fail to understand the delicate balance of science and investigative activity required to successfully work a crime scene. • Incorrectly consider crime scene investigation as a simple, non-scientific process, requiring minimal expertise that anyone can be trained to do. • Illustrated by: The composition of crime scene units by police agencies personifies inherent belief: • Scene investigation is simple, a matter of spreading dusting powder around; shining an ALS or laser to find fingerprints, biological fluids and fibers; collecting the evidence; packaging it and delivering it to an appropriate location, perhaps a crime laboratory. • This too widely held belief is not correct. In fact, As an investigative paradigm … It is WRONG

  5. Crime Scene InvestigationA Scientific-Investigative Endeavor

  6. Why Investigate the Crime Scene? • An obvious response might be, “To find evidence.” • Certainly this happens, but is that all? Is that the sole reason for investigating a crime? For this lecture series, the question is appropriate, and finding evidence is but one important product the scene investigation. • The overriding reason, of course, is to solve the crime. But it is also to solve related crimes. • The scene investigation will not normally solve the crime that day, which is why the scene investigation is the initial step in the process. • There are five reasons for investigating the crime scene • Finding, packaging, preserving evidence being byproduct of the process.

  7. Immediate Purpose of the Scene Investigation • Investigative leads for detectives • Develop specific information - in the form of evidence or investigative logic - to enable a successful prosecution, • Provide exculpatory evidence of innocence, • Locate appropriately significant information to allow a successful and accurate reconstruction. • Identify links to other crimes

  8. Who Should be Investigating Crime ScenesConsider this …

  9. Hypothetical Case

  10. Your Brother Murdered @ home Who Would Want to Lead the Scene Investigation? Police Investigator Highly Experienced Scene Investigator Forensic Scientist (DNA or Trace Evidence Scientist) Criminalist Experienced Scene Investigator

  11. Historically, mixing science with investigators has not been widely popular or accepted by police agencies, although that paradigm is slowly changing. In fact, this has been a point of controversy for decades. In an article titled, Science Versus Practical Common Sense in Crime Detection, in 1931 Al Dunlap, then the editor of The Detective spoke at the 17th International Association of Identification (IAI) in Rochester, New York. At that convention, Captain Duncan Mathewson, the Chief of Detectives of the San Francisco Police Department said, “Much has been said and published about the educated college policeman and detective and it is all bunk. Give me the practical detective with actual experience in handling criminals and criminal cases and with ten such men I will do more work than any college professor or so-called expert can do with one hundred of his trained nuts. Most of those that I have seen couldn’t put a harness on a mule, let alone catch a crook.” Duncan continued, “There is an overabundance of self-styled scientific detectives and crime experts in this country. They would have a gullible public believe they are so scientific that the crooks would respond to engrave d invitations to visit police headquarters and surrender. Just how long the public will stand for this rot is a question.” Dunlap concluded, “In truth, there is no real cause for a misunderstanding between the exponents of modern science and those who emphasize the need of practical common sense methods of crime detection. Science should simply confine its efforts to the solution of all problems that call for special scientific treatment, and never undertake to steal the show, so to speak, by underrating the importance of practical common-sense methods in the general investigation of nearly all cases. And the old time successful crime investigator should welcome every possible assistance of proven value that science has to offer. Science is not, by the wildest stretch of the imagination, a substitute for practical methods, as the public has often been led to believe; instead it is just a most valuable acquisition and potent aid which should go hand in hand with plain practical common sense and good judgment in a combined effort to cope with the difficult crime situation that confronts the law-enforcement agencies in every section of the land.”

  12. Investigators vs Scientists The police-versus-science at crime scenes controversy continues. In an attack on Chisum and Turvey’s book, Crime Reconstruction, Ross Gardner wrote: “Throughout this text, the authors incorporate a class-based ad hominem attack that is directed against anyone associated with law enforcement. Some of these attacks are indirect and veiled as a discussion of objectivity, but others are clear statements that show the authors come with their own very distinct personal bias.” Chisum and Turvey’s response solidifies their beliefs: “The harsh reality is that crime scene processing and documentation efforts are often abysmal if not completely absent. Crime scenes throughout the United States are commonly processed by police-employed technicians or sworn personnel with little or no formal education, to say nothing of training in the forensic sciences and crime scene processing techniques. The in-service training available to law enforcement typically exists in the form of half-day seminars or short courses taught by nonscientists who, on their own, in no way impart the discipline and expertise necessary to process crime scenes adequately for the purposes of reconstruction.”

  13. Attorney General of the United States As Attorney General Janet Reno stated in Crime Scene Investigation – Guide for Law Enforcement, “Actions taken at the outset of an investigation at a crime scene can play a pivotal role in the resolution of a case. Careful, thorough investigation is key to ensure that potential physical evidence is not tainted or destroyed or potential witnesses overlooked. While many agencies have programs in crime scene processing, the level of training and resources available varies from jurisdiction to jurisdiction, as does the opportunity to practice actual investigation.” [1] Reno, Janet, Crime Scene Investigation – A Guide for Law Enforcement. Research Report. U.S. Department of Justice Office of Justice Programs. January 2000, pg. iii.

  14. Mistakes at the Scene • Few consequences for incompetent investigators.? • Crime scene investigation is like live TV. Mistakes –called bloopers – are there for all to see. Unlike live TV, however, • Mistakes at crime scenes are not recorded, they are not funny, and there is no incentive to “own up” to making them. • Censure does not typically exist. • Peer review is akin to the adage, “the fox watching the hen house.” • Mistakes … loses an electrostatic lift of a dust print … who will know? If an investigator over dusts a fingerprint, smudges important evidence, or chooses an incorrect enhancement technique, who will know? • Miss important, potentially exculpatory evidence, who will know? And if such a mistake is uncovered, the only censure might be an embarrassing day in court or a scolding by a prosecutor before trial.

  15. Certification • Should be mandatory and layered. The IAI has a layered crime scene certification program, but I don’t believe it goes far enough. • Current IAI scene certification is for crime scene investigators who are non-scientists. • An additional certification should be in place for more advanced scene investigators and scene scientists • Should include in-depth understanding of the scientific concepts employed and their limitations AND how and when to apply them. • This certification should stress the limitations of the science including when it can be employed and when it will result in ruined or compromised evidence.

  16. Scene Investigation is most critical part of a competent forensic investigation. • Scene: Where the crime takes place • Where the participants - the victim(s), the assailant(s) and the scene(s) - coincide in time and space. • The scene is silent but loud • Physical plant for the human participants and their activity. • The French scientist Edmund Locard is credited, though perhaps a bit overstated and over used, with the statement that “Every Touch Leaves a Trace.“ • An exchange of material – something - physical evidence, large or small, macroscopic or microscopic takes place among the participants. • The Locard Exchange Principle is the essential ingredient of forensic science, which experience confirms. • The premise of the forensic scientist and crime scene investigator who believes that • If evidence can be located and analyzed, a physical connection among the participants can be identified. Hopefully, this connection leads to an outcome that solves the crime.

  17. What is Forensic Science?

  18. Definition • The application of the techniques of science to legal matters, both criminal and civil. • According to Inman & Rudin, without evidence, forensic science could not exist

  19. Forensics • Term inspired by popular TV programs … public equates forensics, forensic science and criminalistics. The term is an integral part of the modern forensic lexicon. • Clearly, though, those who practice “forensics” in the TV sense are not scientists and by definition may not be either criminalists or forensic scientists. • Mostly, they are police investigators who attempt to apply forensic science to locate and enhance evidence at crime scenes as part of the crime scene investigation • However, because of the widespread application of the term, it has acquired an umbrella-like connotation.

  20. Forensics Forensic Science (AAFS) Non-Scientific Disciplines Scientific Disciplines Pathology Jurisprudence Psychology Dentistry etc Toxicology Anthropology Entomology Chemistry Biology etc Criminalistics Scene Investigations

  21. Forensics An umbrella term applied to investigative professionals who apply standard techniques to answer questions relating to evidence in crimes.

  22. A Typical Scene Investigation Police Department Scene security Evidence collection Scene documentation Mayor Crime Scene What’s Missing??? Science! EMS Contaminates Scene Ascertain medical facts Cause Circumstance Manner Medical Examiner MLI’s

  23. Two Fundamental Principles of Forensic Science

  24. The Origin of EvidencePrinciple of Divisible Matter The Scene Victim Perpetrator Divided Matter At Scene Left as Evidence Original Source of Divisible Matter Fracture Takes Place Divided Matter Remains With Original Source Inman & Rudin

  25. The Locard Exchange Principle Evidence Victim Perpetrator Scene A Transfer of Anything Among All

  26. Criminalistics

  27. A Connection with the Law • Many consider forensic science and the law integrally bound together … • Forensic laboratory analyses conducted in crime laboratories by scientists • The evidence comes to the laboratory as part of an investigation, usually criminal. • However - The court reference of many authors is not entirely appropriate. • Criminalists are involved in an investigation to examine physical evidence which may or may or may not have legal implications

  28. Criminalistics • More than a profession of scientists who examine evidence by employing the principles of science and the scientific method. • It is both science and a philosophy • A holistic approach to an analytical strategy and interpretation of results obtained from the analysis of the evidence within the framework of an entire case.

  29. What Does a Criminalist Do? • Pieces together fragments of facts • to arrive at testable hypotheses. • Without the holistic and scientific, it is impossible to investigate a crime scene properly, evaluate an analytical laboratory strategy, or to reconstruct the events of a crime. • This is true because criminalistics considers all the information in a case, not simply the analysis of a single piece of evidence. • As such, it is an amalgam of the principles of science, logic, critical thinking and experience. From this, perhaps a working definition of criminalistics might be: • Criminalistics is a scientific profession whose members embrace a holistic philosophy encompassing the principles of science, the scientific method, and logic with respect to the analysis of evidence and its relationship to a set of alleged facts

  30. The Forensic DNA Biologist Example • The forensic DNA biologist who accepts a cut-out from a scientist (or scene investigator) who first screened the evidence for the presence of, say semen, and then performs DNA analysis is not a criminalist. • In fact, h/she is a scientist who conducts scientific tests on samples received into the laboratory, albeit it evidence, which is not unlike the medical technologist who is given a blood sample to determine cholesterol levels in a clinical laboratory. • There may be little or no thought or a lot of thought concerning the factual information in the case. • However, the scientist who screened the evidence for the presence of biological evidence may have been practicing criminalistics because during the examination of that evidence, there should have been consideration of the origin of the evidence, its relationship to the case history, an evaluation of the stain’s location and pattern and finally a determination of the appropriateness for DNA analysis. • In other words, the location of the biological evidence and its physical appearance might have dictated other analytical path. • For the DNA analyst described above, the resulting DNA profile may be crucial for obtaining a successful prosecution, but the end product of the DNA analysis, that is generating the DNA profile, was not the practice of criminalistics.

  31. Evidence What it is How it’s Manifested at the Scene

  32. About Evidence: Read This Carefully • “Wherever he steps, whatever he touches,whatever he leaves, even unconsciously,will serve as silent witness against him.Not only his fingerprints or his footprints,but his hair, the fibers from his clothing,the glass he breaks, the tool mark heleaves, the paint he scratches, the blood orsemen he deposits or collects. All of theseand more bear mute witness against him.This is evidence that does not forget.  It isnot confused by the excitement of the moment.  It is not absent because humanwitnesses are, it is factual evidence, physical evidence cannot be wrong, it cannotperjure itself; it cannot be wholly absent,only its interpretation can err.  Only humanfailure to find it, study and understand it,can diminish its value.'  (Harris vs. Unites States,331 US 145, 1947) Dr. Paul Kirk

  33. Generally:Two Kinds of Evidence Testimonial: given in the form of statements made under oath usually in response to questioning (In Great Britain, it’s called: “Giving Evidence”) Physical: something that is real & can take any form

  34. EvidenceWebster - 2006 • Something legally submitted to a competent tribunal as a means of ascertaining the truth of any alleged matter of fact under investigation • Something legally submitted to a competent tribunal as a means of ascertaining the truth of any alleged matter of fact under investigation

  35. What is Evidence? What Do Other Authors Say? • In this course, we are concerned with how crime scene investigators and forensic scientists/criminalists perceive evidence. • Authors of most of the widely read texts fail to include an in depth discussion of evidence. They choose instead to offer overly simplistic definitions, if any at all. • Saferstein: A single sentence, • “The examination of physical evidence by a forensic scientist is usually undertaken for identification or comparison.”

  36. EvidenceSuzanne Bell – Encyclopedia of Forensic Science “Broadly speaking, any type of tangible evidence as opposed to something such as the testimony of an eyewitness. Physical evidence can be anything, from a microscopic trace of dust to a car, but there are some generalizations that can be made. Physical evidence must be documented, collected, marked, transported, and stored in a manner consistent with its type.”

  37. EvidenceFisher – Techniques of Crime Scene Investigation “Physical evidence can take any form. It can be as large as a house or as small as a fiber. It can be fleeting as an odor or as obvious as the scene of an explosion. In fact, the variety of physical evidence that may be encountered in an investigation is infinite.” l “… something submitted to a competent tribunal as a means of ascertaining the truth of any alleged matterof fact under investigation before it.” ,

  38. Dr. Bill Eckert “Demonstrative or physical evidence is something which may be seen, heard, touched, smelled or tasted by the jury itself.” “Thus physical evidence is always derivative of some sort of testimony.” Eckert – Introduction to Forensic Science Dr. Henry Lee “Physical evidence can be classified according to its physical state, by the type of crime, by the nature of the evidence, by its composition, or by the types of question to be resolved [investigative question not legal question], etc. Lee, et al – Crime Scene Handbook - 2005

  39. Vernon Geberth “ …Anything and everything should be considered as evidence. Whether this evidence is physical or testimonial, it must be preserved, noted, and brought to the attention of the investigators.” Geberth – Practical Homicide Investigation

  40. Inman and Rudin • Introduce the concept of evidence -- cite what they refer to as a “unifying paradigm of forensic science,” “divisible matter”, which they believe is necessary in order to invoke the transfer principle attributed to Edmund Locard. • They believe that evidence and any discussion about it is really a conversation about forensic science, because considering one implies a discussion about the other. • They also believe that the concept of evidence may be profession defining: • Evidence defines the profession of forensic science, such that without evidence, forensic science cannot exist. • Certainly, too, without forensic science, evidence cannot be interpreted correctly for the trier of fact. • Never offer an in depth discussion except to consider that, • “The law defines evidence only by its relevance.” • Interesting because it considers the concept of evidence as something that has meaning but forces it into a legal format, which might not be entirely true.

  41. Ross Gardner “…anything that tends to prove or disprove a fact in contention.”

  42. Working Definition of Evidence Anything associated with an incident that may be collected, described, photographed, analyzed or reasoned about and which may be introduced into a legal proceeding in order ascertain theground truth of an issue.

  43. Evidence Dynamics

  44. Evidence DynamicsAn Investigative Concern • Influence on physical evidence • Changes • Relocates • Obscures • Obliterates • Regardless of Intent • Begins with the crime & ends @ adjudication

  45. Evidence DynamicsInfluences on Evidence • Offender Actions • Victim Actions • Secondary Transfer • Witnesses • Weather/climate • Decomposition • Insect Activity • Animal Predation • Fire • Suppression efforts • Police • EMT's • Scene Investigators • Forensic Scientists/forensic entomologist/Criminalists • Medical Examiners/coroners

  46. Five Manifestations of Evidence Predictable Effects • Changes to scene or evidence that occur with rhythm or regularity • Provides a factual reference • Forensic entomology • Forensic medicine Unpredictable Effects • Alter the original scene and the evidence & occur in unexpected or random ways • Post incident changes that can be misinterpreted • Bystanders/witnesses • EMT • Police entry to scene

  47. Manifestation of Evidence Transitory Effects • Fleeting evidence • Requires diligence by investigator – first officer – to observe & note • Provides a factual reference • Odors • Melting Ice in glass • Tire signature on roadway Relational Detail • Investigator’s ability to correlate evidence @ the scene • Movement or weather can alter physical location of evidence • Void patterns • Cluster of shell casings • Muzzle-target distance estimation

  48. Manifestation of Evidence Functional Detail • Whether things that should work actually do • The gun at the scene • The locks on the doors • Clock that stopped

  49. Logic at the SceneA Case Example

  50. Case Facts: Secondary Response • Thought to be a homicide based on “witness” account • Saw struggle • Saw someone leaning across seat from passenger side • Gunshot wound to right side of head • Weapon missing • CSI had already processed car • Passenger door removed • Other considerations • Brother recently committed suicide • Had been drinking heavily