1. Chapter 3: Physical Evidence “You can learn a lot by just watching.” —Yogi Berra, former New York Yankees catcher and sage

2. Chapter 3 1 What is evidence? State 5 examples. Please Do Now

3. Chapter 3 2 Locard’s Exchange Principle Edmond Locard (1877-1966)  “Locard's Exchange Principle” states that whenever two objects come into contact there is a transference of material between them.

4. Chapter 3 3 Types of Evidence Two general types:  Testimonial—a statement made under oath; also known as direct evidence or Prima Facie evidence  Physical—any object or material that is relevant in a crime; also known as indirect evidence. Examples are hair, fiber, fingerprints, documents, blood, soil, drugs, tool marks, impressions, glass. Note: This chapter will focus on physical evidence

5. Chapter 3 4 Reliability of Eyewitness Factors:  Nature of the offense and the situation in which the crime is observed  Characteristics of the witness  Manner in which the information is retrieved Additional factors:  Witness’s prior relationship with the accused  Length of time between the offense and the identification  Any prior identification or failure to identify the defendant  Any prior identification of a person other than the defendant by the eyewitness

6. Chapter 3 5 Eyewitness  A police composite may be developed from the witness testimony by a computer program or forensic artist.  “Perception is reality.”  As a result of the influences in eyewitness memory, physical evidence becomes critical. Faces—a composite program by InterQuest

7. Chapter 3 6 Value of Physical Evidence  Generally more reliable than testimonial  Can prove that a crime has been committed  Can corroborate or refute testimony  Can link a suspect with a victim or with a crime scene  Can establish the identity of persons associated with a crime  Can allow reconstruction of events of a crime

8. Chapter 3 7 Physical Evidence  It would be impossible to list all the objects that could conceivably be of importance to a crime.  Almost anything can be Physical Evidence.  Although you cannot rely on a list of categories, it is useful to discuss some of the most common types of physical evidence.  The purpose of recognizing physical evidence is so that it can be collected and analyzed.  It is difficult to ascertain the weight a given piece of evidence will have in a case as ultimately the weight will be decided by a jury.

9. Chapter 3 8 Common Types of Physical Evidence  Blood, semen, and saliva  Documents  Drugs  Explosives  Fibers  Fingerprints  Firearms and ammunition  Glass  Hair  Impressions  Organs and physiological fluids  Paint  Petroleum products  Plastic bags  Plastic, rubber, and other polymers  Powder residues  Serial numbers  Soil and minerals  Tool marks  Vehicle lights  Wood and other vegetative matter

10. Chapter 3 9 Physical Evidence  Blood, semen and saliva  Documents

11. Chapter 3 10 Physical Evidence  Drugs  Explosives

12. Chapter 3 11 Physical Evidence  Fibers  Fingerprints Silk fibers

13. Chapter 3 12 Physical Evidence  Firearms and ammunition  Glass Refractive index

14. Chapter 3 13 Physical Evidence  Hair  Impressions Dyed human hair Hair shaft comparison Impression foam

15. Chapter 3 14 Physical Evidence  Organs and physiological fluids  Paint Car paint layers 300X

16. Chapter 3 15 Physical Evidence  Petroleum products  Plastic bags

17. Chapter 3 16 Physical Evidence  Plastic, rubber and other polymers  Powder residues Powder residue test

18. Chapter 3 17 Physical Evidence  Serial numbers  Soil and minerals Serial number restoration

19. Chapter 3 18 Physical Evidence  Tool marks  Vehicle lights Honda Tail lights

20. Chapter 3 19 Physical Evidence  Wood and other vegetative matter Mixed pollen Diatoms

21. Chapter 3 20 Common Types of Physical Evidence  Blood, semen, and saliva  Documents  Drugs  Explosives  Fibers  Fingerprints  Firearms and ammunition  Glass  Hair  Impressions  Organs and physiological fluids  Paint  Petroleum products  Plastic bags  Plastic, rubber, and other polymers  Powder residues  Serial numbers  Soil and minerals  Tool marks  Vehicle lights  Wood and other vegetative matter

22. Chapter 3 21 Using Physical Evidence  As the number of different objects linking an individual to a crime scene increases, so does the likelihood of that individual’s involvement with the crime  Also a person may be exonerated or excluded from suspicion if physical evidence collected at a crime scene is found to be different from standard/reference samples collected from that suspect

23. Chapter 3 22 Why Examine Physical Evidence?  The examination of physical evidence by a forensic scientist is usually undertaken for identification or comparison purposes.  Identification has, as its purpose, the determination of the physical or chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit.  A comparison analysis subjects a suspect specimen and a standard/reference specimen to the same tests and examinations for the ultimate purpose of determining whether or not they have a common origin.

24. Chapter 3 23 Identification  to determine the physical or chemical identity with as near absolute certainty as existing analytical techniques will permit  first requires the adoption of testing procedures that give characteristic results for specific standard materials  Once these test results have been established, they may be permanently recorded and used repeatedly to prove the identity of suspect materials  Second, the number and type of tests needed to identify a substance be sufficient to exclude all other substances

25. Chapter 3 24 Common Types of Identification  The crime lab is often requested to identify: 1.Chemical composition of an illicit drug 2.Gasoline in residues recovered from the debris of a fire, or the nature of explosive residues— for example, dynamite or TNT 3.Blood, semen, hair or wood - including a determination for species origin

26. Chapter 3 25 Comparison  A comparative analysis has the important role of determining whether or not a suspect specimen and a standard/reference specimen have a common origin.  Both the standard/reference and the suspect specimen are subject to the same tests.

27. Chapter 3 26 Forensic comparison  A two step procedure: 1.First, combinations of select properties are chosen from the suspect and the standard/reference specimen for comparison. 2.Second, once the examination has been completed, the forensic scientist must draw a conclusion about the origins of the specimens

28. Chapter 3 27 Role of Probability in Forensic Comparison  To comprehend the evidential value of a comparison, one must appreciate the role that probability has in ascertaining the origins of two or more specimens  Probability: the frequency of occurrence of an event  Easy to establish the probability of flipping a coin  Exact probability is impossible to define with many analytical processes

29. Chapter 3 28 Probability For example: Blood FactorsFrequency A 26% EsD 85% PGM 2+2— 2% What is the probability of someone having all three factors? 0.26 X 0.85 X 0.02 = 0.00442 which is Using the product rule: ONLY 0.442% or 1OO or 1 out of 226 people.442

30. Chapter 3 29 Classifying Characteristics  Individual Characteristics  Properties of evidence that can be attributed to a common source with an extremely high degree of certainty  Class Characteristics  Properties of evidence that can only be associated with a group and never with a single source

31. Chapter 3 30 Individual Characteristics  In all cases, it is not possible to state with mathematical exactness the probability that the specimens are of common origin.  It can only be concluded that this probability is so high as to defy mathematical calculations or human comprehension.

32. Chapter 3 31 Evidence Characteristics  Class characteristics—Evidence common to a group of objects or persons  Individual characteristics—Evidence can be identified with a particular person or a single source with an extremely high degree of probability Blood DNA TypingFingerprints

33. Chapter 3 32 Examples of Individual Characteristics 1.the matching ridge characteristics of two fingerprints 2.the comparison of random striation markings on bullets or tool marks 3.the comparison of irregular and random wear patterns in tire or footwear impressions 4.the comparison of handwriting characteristics 5.the fitting together of the irregular edges of broken objects in the manner of a jigsaw puzzle 6.matching sequentially made plastic bags by striation marks running across the bags

34. Chapter 3 33 Class vs Individual Evidence Which examples do you think could be individual evidence?

35. Chapter 3 34 Class vs Individual Evidence  The large piece of glass fits to the bottle—it is individual evidence  These fibers are class evidence—there are millions like them.

36. Chapter 3 35 Class vs Individual Evidence  it is individual evidence— the dental work on the teeth can be used to identify the person  This tape is class evidence—but it could be individual evidence if the striations of the tear match.

37. Chapter 3 36 Class vs Individual Evidence  This tire track is class evidence, as it can be linked to a class of tire —but it could be individual evidence if there are unique impressions.

38. Chapter 3 37 Class Characteristics  Frequently forensic scientists cannot relate physical evidence to a common origin with a high degree of certainty  Evidence is said to possess class characteristics when it can be associated only with a group and never with a single source.  Again, probability is a determining factor.  Nevertheless, the high diversity of class evidence in our environment makes their comparison very significant in the context of a criminal investigation.

39. Chapter 3 38 Class Evidence  A weaknesses of forensic science is the inability of the examiner to assign exact or even approximate probability values to the comparison of most class physical evidence.  For 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?  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.

40. Chapter 3 39 Class Evidence  One of the primary endeavors of forensic scientists must be to create and update statistical databases for evaluating the significance of class physical evidence.  Most items of physical evidence retrieved at crime scenes cannot be linked definitively to a single person or object.  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.

41. Chapter 3 40 Class Evidence  The chances are low of encountering two indistinguishable items of physical evidence at a crime scene that actually originated from different sources.  When one is dealing with more than one type of class evidence, their collective presence may lead to an extremely high certainty that they originated from the same source.  Finally, the contribution of physical evidence is ultimately determined in the courtroom.

42. Chapter 3 41 Crossing Over  Crossing over the line from class to individual does not end the discussions.  How many striations are necessary to individualize a mark to a single tool and no other?  How many color layers individualize a paint chip to a single car?  How many ridge characteristics individualize a fingerprint?  How many handwriting characteristics tie a person to a signature?  These are all questions that defy simple answers and are the basis of arguments.

43. Chapter 3 42 Natural vs. Evidential Limits  There are practical limits to the properties and characteristics the forensic scientist can select for comparison.  Modern analytical techniques have become so sophisticated and sensitive that natural variations in objects become almost infinite.  Carrying natural variations to the extreme, no two things in this world are alike in every detail.  Evidential variations are not the same as natural variations.  Distinguishing variations of evidential use from natural variations is not always an easy task.

44. Chapter 3 43 Forensic Databases  The ultimate contribution a criminalist can make is  The crime lab is on the forefront of the investigation seeking to identify perpetrators  computerized databases link all 50 states and those that link police agencies throughout the world to link a suspect to a crime through comparative analysis

45. Chapter 3 44 Forensic Databases  Integrated Automated Fingerprint Identification System (IAFIS)  a national fingerprint and criminal history system maintained by the FBI 60 million prints on file

46. Chapter 3 45 Forensic Databases  Combined DNA Index System (CODIS)  enables federal, state, and local crime laboratories to electronically exchange and compare DNA profiles - maintained by the FBI

47. Chapter 3 46 Forensic Databases  National Integrated Ballistics Information Network (NIBIN)  Allows firearm analysts to acquire, digitize, and compare markings made by a firearm on bullets and cartridge casings  maintained by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF)

48. Chapter 3 47 Forensic Databases  International Forensic Automotive Paint Data Query (PDQ)  contains chemical and color information pertaining to original automotive paints  maintained by the Forensic Laboratory Services of the Royal Canadian Mounted Police Cross section of Automobile paint

49. Chapter 3 48 Forensic Databases  Shoeprint image capture and retrieval (SICAR)  shoeprint database  computer retrieval system - not maintained by a government agency

50. Chapter 3 49 Reconstruction  The method used to support a likely sequence of events by the observation and evaluation of physical evidence, as well as statements made by those involved with the incident, is referred to as reconstruction.  Crime-scene reconstruction relies on the combined efforts of medical examiners, criminalists, and law enforcement personnel to recover physical evidence and to sort out the events surrounding the occurrence of a crime.

51. Chapter 3 50 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 accounts given by witnesses and/or 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.

52. Chapter 3 51 Reconstruction Physical Evidence is used to answer questions about:  what took place  how the victim was killed  number of people involved  sequence of events A forensic scientist will compare the questioned or unknown sample with a sample of known origin.

53. Chapter 3 52 Summing It Up  Reconstruction is a team effort that involves putting together many different pieces of a puzzle.  The right connections have to be made among all the parts involved so as to portray the relationship among the victim, the suspect, and the crime scene.  If successful, reconstruction can play a vital role in aiding a jury to arrive at an appropriate verdict.  The recognition, collection, and analysis of physical evidence is the foundation to successful reconstruction, but only part of the process.

54. Chapter 3 53

55. Chapter 3 54 Types of Physical Evidence  Transient Evidence—temporary; easily changed or lost; usually observed by the first officer at the scene  Pattern Evidence—produced by direct contact between a person and an object or between two objects  Conditional Evidence—produced by a specific event or action; important in crime scene reconstruction and in determining the set of circumstances or sequence within a particular event  Transfer Evidence—produced by contact between person(s) or object(s), or between person(s) and person(s)  Associative Evidence—items that may associate a victim or suspect with a scene or each other; ie, personal belongings —Lee and Labriola in Famous Cases, 2001

56. Chapter 3 55 Examples of Transient Evidence  Odor—putrefaction, perfume, gasoline, urine, burning, explosives, cigarette or cigar smoke  Temperature—surroundings, car hood, coffee, water in a bathtub, cadaver  Imprints and indentations— footprints, teeth marks in perishable foods, tire marks on certain surfaces  Markings

57. Chapter 3 56 Examples of Pattern Evidence Pattern Evidence—most are in the form of imprints, indentations, striations, markings, fractures or deposits.  Clothing or article distribution  Gun powder residue  Material damage  Body position  Tool marks  Modus operandi  Blood spatter  Glass fracture  Fire burn pattern  Furniture position  Projectile trajectory  Tire marks or skid marks

58. Chapter 3 57 Examples of Conditional Evidence  Light—headlight, lighting conditions  Smoke—color, direction of travel, density, odor  Fire—color and direction of the flames, speed of spread, temperature and condition of fire  Location—of injuries or wounds, of bloodstains, of the victim’s vehicle, of weapons or cartridge cases, of broken glass  Vehicles—doors locked or unlocked, windows opened or closed, radio off or on (station), odometer mileage  Body—position, types of wounds; rigor, livor and algor mortis  Scene—condition of furniture, doors and windows, any disturbance or signs of a struggle

59. Chapter 3 58 Classification of Evidence by Nature  Biological—blood, semen, saliva, sweat, tears, hair, bone, tissues, urine, feces, animal material, insects, bacterial, fungal, botanical  Chemical—fibers, glass, soil, gunpowder, metal, mineral, narcotics, drugs, paper, ink, cosmetics, paint, plastic, lubricants, fertilizer  Physical—fingerprints, footprints, shoe prints, handwriting, firearms, tire marks, tool marks, typewriting  Miscellaneous—laundry marks, voice analysis, polygraph, photography, stress evaluation, psycholinguistic analysis, vehicle identification

60. Chapter 3 59 Forensic Investigations Include some or all of these seven major activities 1. Recognition—ability to distinguish important evidence from unrelated material  Pattern recognition  Physical property observation  Information analysis  Field testing 2. Preservation—collection and proper preservation of evidence

61. Chapter 3 60 Investigations 3. Identification—use of scientific testing  Physical properties  Chemical properties  Morphological (structural) properties  Biological properties  Immunological properties 4. Comparison—class characteristics are measured against those of known standards or controls; if all measurements are equal, then the two samples may be considered to have come from the same source or origin.

62. Chapter 3 61 Investigations 5. Individualization—demonstrating that the sample is unique, even among members of the same class 6. Interpretation—gives meaning to all the information 7. Reconstruction—reconstructs the events of the case  Inductive and deductive logic  Statistical data  Pattern analysis  Results of laboratory analysis —Lee, Dr. Henry. Famous Crimes, 2001