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Transcript
Forensic Science INTRODUCTION What is forensic science? Forensic science is the application of science to criminal and civil laws. This course emphasizes the application of science to those criminal and civil laws that are enforced by police agencies in a criminal justice system. Forensic science owes its origins to many scientists who developed the principles and techniques needed to identify or compare physical evidence. History of Forensic Science Mathieu Orfila (1813) —the father of forensic toxicology; published a treatise. Alphonse Bertillion—devised the first scientific system of personal identification in 1879. Francis Galton—conducted the first definitive study of fingerprints and their classification. Leone Lattes—developed a procedure to determine blood type from dried bloodstains. Calvin Goddard—used a comparison microscope to determine if a particular gun fired a bullet. Albert Osborn—developed the fundamental principles of document examination. History of Forensic Science Walter McCrone—utilized microscopy and other analytical methodologies to examine evidence. Hans Gross —wrote the first treatise describing the application of scientific principles to the field of criminal investigation. The “father of criminal investigation.” Edmond Locard—incorporated Gross’ principles within a workable crime laboratory. Locard’s Exchange Principle—states that when a criminal comes in contact with an object or person, a cross-transfer of evidence occurs. “Every contact leaves a trace.” Locard’s Exchange Principle The Locard Exchange Principle states that whenever two objects come into contact, a mutual exchange of matter will take place between them. VICTIM SUSPECT PHYSICAL EVIDENCE OBJECT CRIME SCENE Corpus Delicti “Body of the Crime” A crime must have been proven to be committed before someone is convicted of having committing the crime. You must prove That a crime occurred That the person charged with the crime was responsible for the crime Sources of physical evidence Body Suspect Primary and secondary crime scenes Facets of Guilt The common summation of the three aspects of a crime that must be determined before a conviction Means – the ability to have committed a crime Motive – the reason for committing the crime (This does not have to be proven in the court of law but it is what everyone wants to know!) Opportunity – time or availability to have committed the crime The court cannot convict on these three things along … the prosecution must present evidence! Where is evidence analyzed? How long does it take to analyze evidence? What is the CSI Effect? The CSI effect, also known as the CSI syndrome and the CSI infection, is any of several ways in which the exaggerated portrayal of forensic science on crime television shows such as CSI: Crime Scene Investigation influences public perception. CSI Effect CSI Disney The Crime Lab 16 The development of crime laboratories in the United States has been characterized by rapid growth accompanied by a lack of national and regional planning and coordination. At present, approximately 400 public crime laboratories operate at various levels of government—federal, state, county, and municipal. FBI Crime Lab 1932 – FBI Crime Lab founded. The Crime Lab 18 The ever increasing number of crime laboratories is partly the result of the following: Supreme Court decisions in the 1960s responsible for police placing greater emphasis on scientifically evaluated evidence. Crime laboratories inundated with drug specimens due to accelerated drug abuse. (All illicit drug seizures must be sent to forensic laboratory for confirmatory chemical analysis before the case can be adjudicated. The advent of DNA profiling. Increasing crime rates coupled with fewer confessions because people know their rights! Major Federal Crime Labs Federal Bureau of Investigation (FBI) Drug Enforcement Administration (DEA) Bureau of Alcohol, Tobacco, Firearms, and Explosives US Postal Inspection Service Basic Services in Full Service Labs 20 The technical support provided by crime laboratories can be assigned to five basic services. Physical Science Unit incorporates the principles of chemistry, physics, and geology to identify and compare physical evidence. (drugs, soil, glass, paint) Biology Unit applies the knowledge of biological sciences in order to investigate blood samples, body fluids, hair samples. Firearms Unit investigates discharged bullets, cartridge cases, shotgun shells, and ammunition. Basic Services 21 Document Unit provides the skills needed for handwriting analysis and other questioneddocument issues. Photography Unit applies specialized photographic techniques for recording and examining physical evidence. Optional Services 22 Optional Services by Full-Service Labs Toxicology Unit examines body fluids and organs for the presence of drugs and poisons. Latent Fingerprint Unit processes and examines evidence for latent fingerprints. Polygraph Unit conducts polygraph or lie detector tests. Voiceprint Analysis Unit attempts to tie a recorded voice to a particular suspect. Evidence-Collection Unit dispatches specially trained personnel to the crime scene to collect and preserve physical evidence. The forensic scientist Skills of a Forensic Scientist 24 A forensic scientist must be skilled in applying the principles and techniques of the physical and natural sciences to the analysis of the many types of evidence that may be recovered during a criminal investigation. A forensic scientist may also provide expert court testimony. An expert witness is an individual whom the court determines possesses knowledge relevant to the trial that is not expected of the average person. (An ordinary witness must give testimony on events or observations that arise from personal knowledge. Testimony must be factual and cannot give opinions. Skills of a Forensic Scientist 25 The expert witness is called on to evaluate evidence based on specialized training and experience that the court lacks the expertise to do. The expert will then express an opinion as to the significance of the findings. Forensic scientists also participate in training law enforcement personnel in the proper recognition, collection, and preservation of physical evidence. Analysis of Physical Evidence Forensic scientists must be aware of the demands and constraints imposed by the judicial system. The procedures and techniques used in a laboratory must not only rest on firm scientific foundation but also must satisfy the criteria of admissibility that have been established by the courts. The Frye Standard The Frye v. United States decision set guidelines for determining the admissibility of scientific evidence into the courtroom. To meet the Frye standard, the evidence in question must be “generally accepted” by the scientific community. 27 Frye Not Absolute 28 However, in the 1993 case of Daubert v. Merrell Dow Pharmaceutical, Inc., the U.S. Supreme Court asserted that the Frye standard is not an absolute prerequisite to the admissibility of scientific evidence. Trial judges were said to be ultimately responsible as “gatekeepers” for the admissibility and validity of scientific evidence presented in their courts, as well as all expert testimony. The Daubert Criteria 29 In Daubert, the Supreme Court offered some guidelines as to how a judge can gauge scientific evidence: 1) Whether the scientific technique or theory can be (and has been) tested. 2) Whether the technique or theory has been subject to peer review and publication. 3) The technique’s potential rate of error. 4) Existence and maintenance of standards controlling the technique’s operation. 5) Whether the scientific theory or method has attracted widespread acceptance within a relevant scientific community. Hmmmm … Special Forensic Science Services 31 A number of special forensic science services are available to the law enforcement community to augment the services of the crime laboratory. These services include forensic pathology, forensic anthropology, forensic entomology, forensic psychiatry, forensic odontology, computer science, forensic engineering, among many others. Switching gears … Anytime there is a death associated with accidents, violence, injuries, or unexplained causes, we look to the body to provide clues as to what happened and how it happened. “This is the place where death rejoices to help those who live.” Special Forensic Science Services Forensic Pathology involves the investigation of unnatural, unexplained, or violent deaths. Forensic pathologists in their role as medical examiners or coroners are charged with determining cause of death. The forensic pathologist may conduct an autopsy which is the medical dissection and examination of a body in order to determine the cause of death. 33 Medical Examiner vs. Coroner There are two systems of death investigation in the US today. A medical examiner is a medical doctor, usually a pathologist, who is appointed by the governing body of the area. A coroner is an elected official who usually has no special medical training but is legally responsible for overseeing death investigations. **Any responsibilities the coroner cannot complete, will be contracted out to a forensic pathologist. Medical Examiner’s Responsibilities Identify the deceased. Establish the time and date of death. Determine a medical cause of death – the injury or disease that resulted in the person dying. Determine the mechanism of death – the physiological reason that the person died. Classify the manner of death. Natural Accidental Suicide Homicide Undetermined Notify the next of kin. Sign the death certificate. So … One can die from a massive hemorrhage (mechanism of death) due to a gunshot wound through the head (cause of death) as a result of being shot (homicide), shooting oneself (suicide), dropping a gun and discharging it (accident), or not being able to tell (undetermined). All of which are manners of death. Something to think about … In our legal system, injuries always take precedence over disease for determining the cause of death. Ex) A person could have severe heart disease long before they are mildly assaulted. In a normal person, the assault might have caused little more than a bruise but in this case, it could have triggered a heart attack that led to the person’s death. The cause of death in this case would have been determined to be from the blunt force trauma (assault), with the heart disease as a contributing cause. The manner of death here would be homicide. Similarly, if a person is shot and recovers but dies 20 years later from pneumonia, it might be determined that the death was cuased by the older gunshot injury with pneumonia as a contributing factor. This would mean the death is classified as a homicide. Now you tell me … A motorcycle accident leaves a man with a fractured tibia that is set in the hospital and the person recovers. Over a number of years, however, an infection of the broken bone sets in that ultimately develops into a cancer in the open space left in the bone by the original accident. The cancer goes undetected for years until it metastasizes elsewhere in the body. The cancer eventually kills the man more than twenty years after the original motor cycle accident. What would YOU determine to the be manner, cause, and mechanism of death? Answer: Manner: accidental Cause: cancer Mechanism: metastatic squamous cell carcinoma with contributing infection Let’s talk about dead bodies … The Corpse “The way I see it, being dead is not terribly far off from being on a cruise ship. Most of your time is spent lying on your back. The brain has shut down. The flesh begins to soften. Nothing much new happens, and nothing is expected of you.” --Mary Roach. Stiff. W. W. Norton & Company. 2003 Stiff: The Curious Lives of Human Cadavers The book covers 12 topics: Practicing cosmetic surgery on cadaver heads Body snatching and the early years of human dissection The nature of decomposition Cadavers for use as crash test dummies Using cadavers to analyze a crash site Army tests on cadavers Crucifixion experiments Beating heart cadavers, the soul, and being buried alive Decapitation and human head transplant Cannibalism in the name of medicine New alternatives to burial and cremation The author's views on her own remains After death … After a human body expires there are several stages of death. Rigor mortis results in the shortening of muscle tissue and the stiffening of body parts in the position at death (occurs within the first 8 hours and usually disappears within 36 hours though can linger up to 72 hrs). Livor mortis results in the settling of blood in areas of the body closest to the ground (begins immediately on death and continues up to 12 hours). After 12 hours the lividity is FIXED. Algor mortis results in the loss of heat by a body (a general rule, beginning about an hour after death, the body loses heat by 1 to 1-1/2 degrees Fahrenheit per hour until the body reaches the environmental temperature). The Body Rigor Mortis Temperature of the Body Stiffness of the Body Time since death WARM NOT STIFF Less than 3 hours WARM STIFF Between 3 – 8 hours COLD STIFF Between 8 – 36 hours COLD NOT STIFF More than 36 hours Rigor Mortis Livor Mortis Livor Mortis The Body Algor mortis The cooling of the body that occurs after death, assuming the ambient temperature is lower than the body temperature. Generally the cooling rate is about 1.5°F per hour. (Normal body temperature is 98.6°F.) Autopsy An autopsy is a postmortem examination of a body in order to answer the following questions: Who are you? When did you become ill or hurt and when did you die? Where did you get hurt and where did you die? Did you die as a result of an accident, violence, natural causes or some combination of these reasons? If violence was completely or partially responsible for your death, was it from suicide, accident, homicide, or other reasons? If someone killed you, who did it? Autopsy Y incision Examination and dissection of all internal organs including brain Hands Smells Eyes Confessions of a Medical Examiner Forensic Odontology The application of dentistry to human identification problems. Forensic odontologists are dentists who specialize in the forensic aspect of their field. They are concerned with the ID of persons based upon their dentition, usually in cases of otherwise unrecognizable bodies or in mass disasters. They also analyze and compare bite mark evidence. Forensic Anthropology Personal identification based on bodily remains (particularly skeletal) Practitioners are anthropologists who are interested in forensic science. Other areas of forensic anthropology include Maintaining databases on bodily structures as functions of race, sex, age, stature, etc. Facial reconstruction Forensic Toxicology The determination of toxic substances in human tissues and organs. Much of the work concerns the role toxic agents may have played in causing or contributing to the death of a person. Trace Evidence Analysis Includes all the areas of trace and transfer evidence, such as Soil and glass Hair and fibers Blood Physiological fluids Arson accelerant and explosive residues Drug identification Different patterns and imprints Questioned Document Examination The comparison and interpretation of Handwriting Mechanically produced material (typing, printing) Photocopied material The analysis of paper, inks, and other materials to produce documents. Firearm and Toolmark Examination Firearm identification Comparison of markings on bullets, cartridge cases, and shell cases. Determining if a bullet has been fired from a particular weapon. Toolmark examinations are concerned with the association of a particular impression with a particular tool. Fingerprint Examinations Classification of fingerprints Maintaining fingerprint databases Development and lifting of latent prints Comparisons of known and unknown fingerprints to determine a match Forensic Entomology Insect activity is used to estimate the time of death. Specific insects present in the body and how long a body has been left exposed can be determined by examining the stage of development of fly larvae. What are the goals of a forensic scientist? The general goals of a forensic scientist are Recognition of physical evidence Identification of physical evidence Individualization of physical evidence Reconstruction of the crime (R.I.I.R.) Recognition Although it may seem obvious it is important to be able to recognize what is and is not physical evidence. Almost anything can be physical evidence and it is very dependent on the type of crime committed. With practice and experience evidence recognition becomes easier. Beware … submitting too much evidence is just as bad as submitting too little! Identification Identification of physical evidence may be regarded as a classification scheme. Evidence is assigned into categories containing like items. Initial categories are broad and then narrowed down as more information is obtained Example Blue substance Blue paint Blue car paint Blue car paint from Ford Manufacturing Company Blue car paint from Ford produced 1998-2000 Blue car paint from Ford produced 1998-2000, used on Mustang and Explorer. Class Evidence Class evidence is evidence that can be associated with a particular group. Class characteristics are the properties that all the members of a certain group of objects or substances have in common. The “paint” is condsidered CLASS EVIDENCE. Examples of Class Evidence Single layered paint Soil Glass fragments too small to fit back together Hairs fibers The Value of Class Evidence Many lawyers try to discredit class evidence because it cannot be limited to just one possible source, however class evidence DOES HAVE VALUE. Look around the room, most have different clothes on. If I were to pick a fiber from one person’s clothes in this room, that fiber could possibly pick out the single source or at least narrow the field. Some class evidence holds little forensic value, such as fiber from jeans or white cotton shirts … they are too common!! Individualization Individualization is unique to forensic science. It refers to the idea that a particular sample is unique, even among members of the same class. It may also refer to the demonstration that a questioned piece of physical evidence and a similar known sample have a common origin. More than CLASS In addition to class characteristics, objects and materials possess individual characteristics that can be used to distinguish members of the same class. The nature of these individual characteristics varies from one type of evidence to another, but forensic scientists try to take advantage of them in effort to individualize a piece of physical evidence by some type of comparison process. Only a few types of physical evidence (primarily physical pattern evidence) can be truly individualized. Evidence that contains Individualizing Characteristics Fingerprints Handwriting Bullets Toolmarks Shoeprints Tire prints Glass fragments that can be matched. Problems with Words Identification is sometimes used to mean personal identification Fingerprints for example, can be used to “identify” an individual The terminology is unfortunate, since this process is really “individualization.” Likewise, dental evidence and dental records are used in “identifying” dead bodies … when they are really individualizing. The GOAL … Ultimate goal would be to move all class evidence to individualistic which is not very likely Hair is trying to make the move … something like paint probably never will. For human evidence to be individualistic, the odds of two people matching the same piece of evidence must be 1 in about 7.5 billion, which is the population of the earth. Is DNA individualistic? Because of identical twins, DNA is not considered individualistic!! Identical twins do have different fingerprints! Reconstruction Reconstruction refers to the process of putting the “pieces” of a case or situation together. The objective is to reach an understanding of a sequence of past events based on the record of physical evidence. Identification and individualization of physical evidence plays a crucial role in providing data for reconstructions.