Forensic Science Study Guide By: Candice Bentham

Transcription

1 Forensic Science Study Guide By: Candice Bentham Video I Lecture I

2 By: Candice Bentham How was the Locard's Exchange Principle illustrated in the video we watched in class? Within the Case the suspect manage to remain anonymous by taking any type of trace evidence on the victims. However with the eyewitness account of her experience with the suspect they forensic evidence began to share similarities among the group of victims. According to Locard s Theory, once a person comes into contact with an object or another person a cross transfer of physical evidence occurs. In the Case with the suspect crime science investigators found bacteria on the victim body that shared similar traits to bacteria that was found on the floor of the suspect s car. Concluding that the chances of these two bacteria begin the same was very low. The transfer of bacteria from the suspects car to the dead body proves that Locard s theory is in fact plausible and can lead to finding the guilty suspect. Murderer: Roger Kibbe Evidence: Blue Carpet fibers Pet hair Fibers on victim s pantyhose Rope white nylon 32 threads per cord red paint particles on the rope - 6 microns

3 Forensic Science Lecture I By: Candice Bentham Forensic Science Definition. The application of science to criminal and civil law The entire concept of forensic science owe its origins to individuals such as Bertillon, Galton, Lattes, Goddard, Osborn, and Locard who developed the principle and techniques needed to identify or compare physical evidence. Initial Scientific Advances Mathieu Orfila. The father of forensic toxicology, in 1814 Orfila published the first scientific treatise on the detection of poison and their effects on animals. Morphology. Is the study of the structure of the living organisms? Alphonse Bertillion. Devised the first scientific system of personal identification in This system was dubbed Anthropometry, which consisted in taking a series of body measurements as a means of distinguishing one individual from another. Francis Galton- Conducted the first definitive study of fingerprints and their classification. His work went on to describe the basic principle that forms the present system of identification by fingerprints. 20 th Century Breakthroughs Leone Lattes. Developed a procedure to determine blood type from dried bloodstains. Albert Osborn. Was the first person to develop the fundamental principle of document examination Edmond Locard. Was a Frenchman whom demonstrated that when a criminal comes in contact with an object or person a cross transfer of evidence occurs. o He strongly believed that every criminal can be connected to a crime by dust particles carried from the crime scene. The most significant modern advances of in forensic science has been the discovery and refinement of DNA typing in the late 20 th and early 21 st centuries. Sir Alec Jeffrey. Developed the first DNA profiling test in 1984 Another recent development in forensic is the establishment of computerized database on physical evidence such as fingerprints, marking on bullets and shell casing and DNA. Crime Laboratories The steady advances in forensic science during the 20 th century led to the establishments of the first facilities specifically dedicated to forensic analysis of criminal evidence. o The supreme court decision in the late 60s responsible for police placing greater emphasis on scientifically evaluated evidence o Crime lab inundated with drug specimens due to accelerated drug abuse o The advent of DNA profiling The technical support provided by the crime lab can be assigned by 5 basic services o Physical science unit. Incorporates the principle of chemistry, physics, and geology to identify and compare physical evidence. o Biology Unit. Applies the knowledge of biological science in order to investigate blood samples, body fluid, hair, and fiber samples.

4 o o o Firearms Unit. Investigates discharged bullets cart Document examination Unit. Studies the handwriting and typewriting on questioned documents. Photography unit. A complete lab examines and records physical evidence. It may require some high level photographic techniques. Optional Services provided by full crime 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 Scientific Method Formulate a question worthy of investigation. Formulate a reasonable hypothesis to answer the question. Test the hypothesis through experimentation. Upon validation of the hypothesis, it becomes suitable as scientific evidence. Skills of a forensic scientist 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. 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. Analyzing Physical Evidence The three major avenues available to police for assistance in solving a crime are; o Confession o Eyewitness or victims accounts of the accident o Physical evidence Science derives from adhering to strict guidelines that ensures careful and systematic collection, organization, and analysis of information- a process called scientific method This method provided a safety net to ensure that the outcome of an investigation is not tainted by human emotion or compromised by distorting, belittling or ignoring contrary evidence

5 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. Daubert Criteria For Admissibility Whether the scientific technique or theory can be tested. Whether the technique has been subject to peer review and publication. The techniques potential rate of error. Existence and maintenance of standards. Whether the scientific theory or method has attracted widespread acceptance within a relevant scientific community. Special Forensic Science Services 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, and forensic engineering. Forensic Psychiatry is an area in which the relationship between human behavior and legal proceedings is examined. Forensic Odontology involves using teeth to provide information about the identification of victims when a body is left in an unrecognizable state. Also investigates bite marks. Forensic Engineering is concerned with failure analysis, accident reconstruction, and causes and origins of fires or explosions. Forensic Computer Science involves the examination of digital evidence.

6 Review from Lecture I Forensic Science Lecture II By: Candice Bentham The Scientific Method Figure out who is the murderer Formulate a Hypothesis Test the hypothesis Using the hypothesis to become a expert witness Skills of a Forensic Scientist A forensic scientist must be skilled with many types of evidence that may be recovered during the investigation A forensic scientist may also contribute to the trial as a expert witness Opinion based on there credentials Daubert Criteria for admissibility Every thing must be reproducible There needs to be standards when testing evidence It needs to be accepted by the relevant to an expert scientist (someone who specializes in that area of study) Chapter II The Crime Scene Physical Evidence As automobiles run on gas, crime labs run on physical evidence The evidence must be documented The forensic science begins at the crime scene The First Steps The first responder is responsible for securing the crime scene The purpose of securing the crime scene is to reduce the chances of adding new evidence, or disturbance in the crime scene The first step must be to take care of the injured victims The first CSI assess the scene, by conducting a preliminary exam and recoding the critical piece to process Recording Methods Sketching out the crime scene, taking pictures, and writing notes are three key methods of recoding the scene Photograph Shows the evidence under unaltered conditions Shows images through a close up view Sketches Once the photos are taken the crime scene the investigator will sketch the scene It depicts physical evident are found, a blue print of the crime scene, scale of the room - What the physical evidence is - Where you found it - What did the investigator do with it

7 Finish sketches. A precise rendering of crime scene usually to scale. This type is not normally competed at the crime scene Notes Taking notes are important guide to where exactly the evidence was found Notes is information for refreshing one s mind before the case reaches trail Investigators have a limited amount of time to record The Preliminary Exam The lead investigator will stat the processing in the crime scene There are different search patterns selected will normally depend on the size If there is a large area the best method to use is strip line or grid method For more circular area a spiral is best. Why start from the outside? The reason is to collect all the evidence as you go along The Search If the object has trace evidence it is best to take it to the lab for further analysis By taking small amounts of these trace evidence Beyond the Crime Scene The search for the physical evidence must extend beyond the crime scene The medical examiner or coroner will carefully examine the victim to establish a cause and a manner of death Is their any evidence to the tissue, internal bleeding, to determine the cause of death Packaging Each different item or similar items collect at different locations must be placed in separate containers Hair can be placed in small containers that keeps the evidence safe Chain of Custody A list of all person who come into contact with evidence that is related to the case Continuity of Possession. Must be established whenever the evidence is presented in the court as an exhibit Every person that comes in contact with the examined evidence must be accounted for. Obtaining Reference Samples Are standard that are from the scene; ie possible suspects, witnesses There should be samples that can be compared from the scene and from the manufactured material or from a person Special Forensic Science Services Forensic Pathology involves the investigation of unnatural, unexplained, or violent deaths The forensic pathologist may conduct an autopsy, which is the medial dissection and examination of a body in order to determine the cause of death

8 Stages of Death Rigor Mortis. Results in the shortening of muscle tissue and the stiffening of the body parts in the position at death occurs within the first 24hrs and disappears within 36hrs. 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 12hrs Algor Mortis. Results in the loss of heat by the body- begins an hour after death and the by loses heat by degree F per hour. Forensic Psychiatry. Is a specialized area that examines the relationship between the human behavior and the legal proceedings In terms of civil cases it can determine whether a person is competent to make decisions about preparing a will or refusing medical treatment. Also determining if a defendant are competent to stand trial Forensic Odontology Practitioner help identity victim based on dental evidence when the body is left in a unrecognizable state. Forensic Engineering Are concerned with the failure analysis accident reconstruction and causes and origins of fires and explosions Forensic computer and digital analysis This is a new and fast growing field that involves identifying, collecting, and examining information derived from computers and other digital devices. Law enforcements aspect of this work normally involves recovering deleted or overwritten data from computer s hard drive and tracking hacking activities within a compromising system. Forensic Anthropology The concern with the identification and examination of human skeletal remains. Bones can tell age, and for babies (skull formation), gender (male vs. female) Forensic Entomology The study of insect and their reaction to a criminal investigation used to estimate the time of death Blow Flies, are the first at the scene.

9 Chapter III Physical Evidence Forensic Science Lecture III By: Candice Bentham Physical Evidence Almost anything can be physical evidence The purpose of recognizing physical evidence is so that it can be collected and analyzed It is difficult to determine whether evidence is valid or not unless it is collected and weighted by the jury in the case Types of Physical Evidence Blood, semen and saliva Documents Drugs Fibers Fingerprints Powder Residues Petroleum Products Paint Plastic bags Soil and Minerals Tool marks Plastic, Rubber, and other polymers Wood and other vegetative matter Vehicle lights Glass Hair Impressions Organ and physiological fluids Firearms and ammunition Explosive Purpose of examining physical evidence The propose of determining of the physical or chemical identity of a substance with as near absolute certainly as existing analytical techniques will permit Identification The object of identification is to determine the physical or chemical identity with as near absolute certainty as existing analytical tech will permit Fingerprints and DNA are good for identification Comparison analysis Subjects that are reference specimens to the specimen found at the crime scene. The ultimate purpose to determine whether or not they have a common origin What needs to be analysis first, a combination of selected properties are chosen from the suspect and standard for comparison First, combinations of select properties are chosen from the suspect and the standard reference specimen for comparison Second, once the examination has been completed the forensic scientist must be prepared to render a conclusion with respect to the origins. Role of Probability To comprehend the evidential values of a comparison one must appreciate the roles that probability has in ascertaining the origins of two or more specimens Simply defined probability is the frequency of occurrence of an event Classifying Characteristics Individual Characteristics

10 o o o Evidence that can be associated to a common source with an extremely high degree of probability is said to possess individual characteristics It all cases it is not possible to state with math exactness the probability that the specimens are of common origin It can only be concluded that this probability is so high as to defy math cal or human comprehensions Examples! The matching ridges characteristics of two fingerprints! The comparison of random striation marking on bullet or tool marks! The comparisons or irregular and random wear pattern in tire or footwear impressions! The comparisons of handwriting characteristics Class Characteristic o Evidence associated only with a group is said to have a class characteristics o Surprising to the inexperienced forensic scientist is the frequent inability of the lab to relate physical evidence to a common origin with a high degree of certainty o Evidence is said to possess class characteristics when it can be associated only with a group and never with a single source o One of the current weaknesses of forensic science is the in ability of the examiner to assign exact or even approximate probability values to the comparison of most class physical evidence Example! What is the probability that a nylon fiber originated from a particular sweater or that a paint chip came from a suspect car in a hit and run o There are very few statistical data available from which to derive this information, and in a mass-produced world, gathering this kind of data is increasingly elusive. o One of the primary endeavors of forensic scientists must be to create and update statistical databases for evaluating the significance of class physical evidence. o Most items of physical evidence retrieved at crime scenes cannot be linked definitively to a single person or object. o The value of class physical evidence lies in its ability to provide corroboration of events with data that are, as nearly as possible, free of human error and bias. Crossing Over Crossing over the line form class to individual does not end the discussions How many colour layers individualize a paint chip to a single car How many handwriting characteristics tie a person to a signature Natural vs. Evidential Limits There are practical limits to the properties and characteristic the forensic scientist an select for comparison Modern analytical techniques have become so sophisticated and sensitive that natural variations in object become almost infinite Evidential variations are not the same as natural variations

11 Using physical Evidence As the number of different object linking an individual to a crime scene increases so does the likelihood of that individual involvement with the crime Forensic Databases Canadian Version of Databases C.C.R.T.I.S. Canadian Criminal Real Time Identification Services DNA Identification Act (started in 2000)- National DNA DataBank (U.S equivalent CODIS) They have convicted offender DNA Index and Crime Scene Index (CSI) C.I.B.I.N- Canadian Integrated Ballistics Identification Network Reconstruction The method used to support a likely sequence of event by the observation and evaluation of physical evidence as well statement made by those involved wit the incident is referred to as reconstruction Crime Scene reconstruction relies on the combined effort of medical examiners, criminalist, and law enforcements personnel to recover physical evidence and to sort out the events surround the occurrence of a crime. The Role of physical Evidence The physical evidence left behind at a crime scene plays a crucial role in reconstructing the events that took place surrounding the crime Although the evidence alone does not describe everything that happened it can support or contradict account given by witnesses and suspects Information obtained from physical evidence can also generate leads and confirm the reconstruction of a crime to a jury. The collection and documentation of physical evidence is the foundation of a reconstruction. Common Types of Identification They need to identify what might have started the accident Determination of species The crime lab is frequently requested to identify the chemical composition of an illicit drug

12 Forensic Science Lecture IV Properties of Matter and glass analysis By: Candice Bentham Density Def Mass Volume Emersion method. The difference between old volume level and new volume level Refractive Indices. Seeing the edge lines. Means light is bending and therefore it is not the same type of glass. Comparing reference to suspects glass Physical vs. Chemical Properties The forensic scientist must constantly determine those properties that impart distinguishing characteristics to matter giving it a unique identity The forensic scientist must constantly determine those properties that impart distinguishing characteristics to matter, giving it a unique identity. Physical properties such as weight, volume, color, boiling point, and melting point describe a substance without reference to any other substance. A chemical property describes the behavior of a substance when it reacts or combines with another substance. Measurement System Scientists throughout the world use the metric system of measurement. The metric system has basic units of measurement for length, mass, and volume; they are the meter, gram, and liter, respectively. The following are common prefixes used in the metric system: deci, centi, milli, micro, nano, kilo, and mega. The Nature of Matter An element is the simplest substance known and provides the building block from which all matter is composed. Matter is anything that has a mass and occupies space. Two or more elements combine to form a compound. An atom is the basic particle of an element and a molecule is the smallest unit of a compound. States of Matter Matter can be classified according to the physical form it takes. Solid-definite shape and volume Liquid-specific volume, takes the shape of its container Gas/vapor-neither a definite shape nor volume Substances can change from one phase to another without forming a new chemical species, matter is simply being changed from physical state to another. Whenever a situation exists in which a substance can be distinguished by a visible boundary, different phases exist. Theory of Light Two models describe the behavior of light. Light is described as a continuous wave.

13 Light is depicted as a stream of discrete energy particles. When white light passes though a prism, it is dispersed into a continuous spectrum of colors. Waves are described in terms such as: Wavelength, the distance between two successive crests (or one trough to the next trough). Frequency, the number of crests (or troughs) passing any one given point per unit of time. Importance of Physical Properties Temperature is a measure of heat intensity, or the hotness or coldness of a substance. In science, the most commonly used temperature scale is the Celsius scale. This scale is derived by assigning the freezing point of water a value of 0 C and its boiling point a value of 100 C. Weight is the force with which gravity attracts a body. Mass refers to the amount of matter an object contains independent of gravity. Density is defined as the mass per unit volume. (D = M/V) o Density is an intensive property of matter, meaning it remains the o same regardless of sample size. It is considered a characteristic property of a substance and can be used as an aid in identification. Light waves travel in air at a constant velocity until they penetrate another medium, such as glass or water, at which point they are suddenly slowed, causing the rays to bend. The bending of light waves because of a change in velocity is called refraction. Refractive index is the ratio of the velocity of light in a vacuum to that in the medium under examination. o For example, at 25 o C the refractive index of water is This means that light travels times faster in a vacuum than it does in water. Like density, refractive index is an intensive property and will serve to characterize a substance. Glass Fragments Glass is a hard, brittle, amorphous substance that is composed of silicon oxides mixed with various metal oxides. Amorphous solids have their atoms arranged randomly, unlike crystals. Tempered glass is stronger than normal glass due to rapid heating and cooling. Laminated glass found in car windshields has a layer of plastic between two pieces of ordinary window glass. For the forensic scientist, the problem of glass comparison is one that depends on the need to find and measure those properties that will associate one glass fragment with another while minimizing or eliminating other sources. To compare glass fragments, a forensic scientist evaluates two important physical properties: density and refractive index.

14 Flotation Method The flotation method is a rather precise and rapid method for comparing glass densities. In the flotation method, a glass particle is immersed in a liquid. The density of the liquid is carefully adjusted by the addition of small amounts of an appropriate liquid until the glass chip remains suspended in the liquid medium. Immersion Mehtod The flotation and the immersion methods are best used to determine a glass fragment s density and refractive index, respectively. The latter involves immersing a glass particle in a liquid medium whose refractive index is varied until it is equal to that of the glass particle. Analyzing Cracks The penetration of window glass by a projectile, whether it is a bullet or a stone, produces cracks which radiate outward (radial fractures) and encircle the hole (concentric fractures). By analyzing the radial and concentric fracture patterns in glass, the forensic scientist can determine the direction of impact. Analyzing Cracks A high-velocity projectile such as a bullet often leaves a hole that is wider at the exit side, and hence its examination is important in determining the direction of impact. The direction of impact can also be accomplished by applying the 3R Rule: Radial cracks form a Right angle on the Reverse side of the force. The sequence of impacts when there have been successive penetrations of glass, is frequently possible to determine because a fracture always terminates at an existing line of fracture. Collection of Glass If even the remotest possibility exists that glass fragments may be pieced together, every effort must be made to collect all the glass found. When an individual fit is thought improbable, the evidence collector must submit all glass evidence found in the possession of the suspect along with a representative sample of broken glass remaining at the crime scene. The glass fragments should be packaged in solid containers to avoid further breakage. If the suspect s shoes and/or clothing are to be examined for the presence of glass fragments, they should be individually wrapped in paper and transmitted to the laboratory.

15 Forensic Science Lecture X Crime Scene Reconstruction: Bloodstains By: Candice Bentham Reconstruction The Method used to support a likely sequence of likely by the observation and evaluation of physical evidence as well as statement made by those included with the incident is referred to as reconstruction Crime scene reconstruction relies on the combined effort of medical examiner, criminalist, and law enforcement personnel to recover physical evidence and to sort out the events surrounding the occurrence of a crime Stain Patterns of Blood The crime scene investigator must remember that the location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that produced the bleeding. Surface texture and the stain s shape, size, and location must be considered when determining the direction, dropping distance, and angle of impact of a bloodstain. Surface texture is of paramount importance. In general, the harder and less porous the surface, the less spatter results. The direction of travel of blood striking an object may be discerned because the pointed end of a bloodstain always faces its direction of travel. The impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion. At right angles the blood drop is circular, as the angle decreases, the stain becomes elongated. The origin of a blood spatter in a two-dimensional configuration can be established by drawing straight lines through the long axis of several individual bloodstains. The intersection or point of convergence of the lines represents the origin point. Surface texture is of paramount importance. In general, the harder and less porous the surface, the less spatter results. The direction of travel of blood striking an object may be discerned because the pointed end of a bloodstain always faces its direction of travel. The impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion. At right angles the blood drop is circular, as the angle decreases, the stain becomes elongated. A shooting may leave a distinct gunshot spatter pattern. This may be characterized by both forward spatter from an exit wound and back spatter from an entrance wound. The location of injury, the size of the wound created, and the distance between the victim and the muzzle of the weapon all affect the amount of back spatter that occurs. A cast-off pattern is created when a blood-covered object flings blood in an arc onto a nearby surface.

16 Arterial spray spatter is created when a victim suffers an injury to a main artery or the heart. Commonly, the pattern shows large spurted stains for each time the heart pumps. A pattern created by blood that is expelled from the mouth or nose from an internal injury is called an expirated blood pattern. A void is created when an object blocks the deposition of blood spatter onto a target surface or object. When an object with blood on it touches one that does not have blood on it, this produces a contact or transfer pattern. Examples of transfers with features include fingerprints, handprints, footprints, footwear prints, tool prints, and fabric prints in blood. Documenting bloodstain Evidence Investigators should note, study, and photograph each pattern and drop of blood to accurately record the location of specific patterns and to distinguish the stains from which laboratory samples were taken. The investigator should create photographs and sketches of the overall pattern to show the orientation of the pattern to the scene. Two common methods of documenting bloodstain patterns are the grid method and the perimeter ruler method.

17 Midterm Short Questions Lecture V By: Candice Bentham Chapter 2 Diagram and describe 4 prime search patterns used during a crime scene investigation List and explain the necessary steps to thoroughly record crime scenes List the responsibility of the first offices Chapter 3 List 10 common of the physical evidence Explain the difference between the identification and comparison physical evidence and example Define and site one example of the difference between individual and class characteristics DNA Characteristics using the probability rule Chapter 4 Define and explain the difference between the physical and chemical properties of matter Contrast the difference between solid, liquid, and gas Diagram and describe how to examine glass fractures to determine the direction of impact of a projectile Chapter 10 Explain how texture f a surface can impact the shape of the individual bloodstain How can investigations determine the area of convergence and an area of impact for a given After looking at the blood stain in figure on the board determine the direction of blood travel

18 Case I Shafia Trial Lecture IV By: Candice Bentham Q. Since the recently concluded Shafia trial (for the socalled "honour killings") included the use of glass evidence, I would like you to write a short paragraph explaining how glass evidence was used to support the prosecutions contentions and the conviction. A. Within the Shafia murder trial prosecutors had compile a case with, Physical evidence that can connect the deaths of four family members found in the Rideau Canal to Mr. Shafia and his son (CBC News, 2012). In connection to the eyewitness evidence used to find Mr. Shafia guilty prosecutors also used remains of broken headlight pieces that would become the key element to prosecute Mr. Shafia. The broken headlight was used to link Mr. Shafia s Lexus to the scene where the police found the Nissan used by one of the victims. The evidence found suggested the only reason pieces of Mr. Shafia s car headlight being found near the scene was that there was an exchange (Locard s Theory) of physical evidence from one scene to another, proving Mr. Shafia s initial story of not knowing the whereabouts of his daughter s to be fictitious.