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Physical EvidenceChapter 3

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Physical Evidence Blood, Semen, Saliva Documents Drugs Explosives Fibers Fingerprints Firearms and Ammunition Glass Hair Impressions

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Physical Evidence Organs and Physiological Fluids Paint Serial Numbers Tool Marks Other

Types of Evidence

Probative: any item/fact that can prove a connection to someone or something in case

Prejudicial: any fact, item or suggestion that pertains to a previous incident that will bias jury

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Physical Evidence IdentificationIdentification - Determination of physical or chemical

identity of a substance with as near absolute certainty as the analytical method will permit.– What is the material? How certain is the answer? What

analytical method(s) will give the best answer (multiple methods)?

ComparisonComparison - Compares standard and suspect samples to determine if they have a common origin.– Can the source of the sample be identified? How

certain is the correlation? How many “data points” are necessary to be “certain beyond a reasonable doubt” of the answer (probability)?

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Identification - Determination of the Determination of the physical and chemical identity of a substance physical and chemical identity of a substance with as near absolute certainty as existing with as near absolute certainty as existing analytical techniques will permit.analytical techniques will permit.

Examples: drug analysis, Examples: drug analysis, species determination & species determination & explosive residue that contain explosive residue that contain dynamite.dynamite.

Example: Example: Gas Chromatography Gas Chromatography / Mass Spectrometry (GC/MS). / Mass Spectrometry (GC/MS). Accurate identification of a Accurate identification of a compound.compound.

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Comparisons

Analysis of a suspect specimen WRT Analysis of a suspect specimen WRT a standard/reference (exemplar) a standard/reference (exemplar) specimen to determine whether or not specimen to determine whether or not they have a they have a common origincommon origin..

CommonOrigin?

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Physical Evidence Class (Group) CharacteristicsClass (Group) Characteristics - Properties of - Properties of

evidence that can only be associated with a evidence that can only be associated with a general group and not with a common source. general group and not with a common source. e.g., blood type, paint or dye lot, etc.e.g., blood type, paint or dye lot, etc.

Individual CharacteristicsIndividual Characteristics - Properties of - Properties of evidence that can connect a sample and standard evidence that can connect a sample and standard to a common source (with high probability). to a common source (with high probability). e.g., fingerprints, unusual wear patterns, tool e.g., fingerprints, unusual wear patterns, tool marks, etcmarks, etc.

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Physical Evidence Class (Group) CharacteristicsClass (Group) Characteristics - Properties of evidence

that can only be associated with a general group and not with a common source. e.g., blood type, paint or dye lot, etc. Blood Types

World:Type A - 42%Type B - 8%Type O - 47%Type AB - 3%

US:Type A - 39%Type B - 13%Type O - 43%Type AB - 5%“Bodies of Evidence” Brian Innes

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Class Characteristics

• Properties of evidence that can only be associated with a group and never with a single source.

• Can be used to exculpate a suspect.

• Examples: single-layer paint chip, blood, nylon fiber from a sweater

Where is Waldo?

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Physical Evidence Class (Group) CharacteristicsClass (Group) Characteristics - Properties of - Properties of

evidence that can only be associated with a evidence that can only be associated with a general group and not with a common source. general group and not with a common source. e.g., blood type, paint or dye lot, etc.e.g., blood type, paint or dye lot, etc.

Individual CharacteristicsIndividual Characteristics - Properties of - Properties of evidence that can connect a sample and standard evidence that can connect a sample and standard to a common source (with high probability). to a common source (with high probability). e.g., fingerprints, unusual wear patterns, tool e.g., fingerprints, unusual wear patterns, tool marks, etc.marks, etc.

Example: from “My Cousin Vinny” (20th Century Fox)

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Physical Evidence Class (Group) CharacteristicsClass (Group) Characteristics - Properties of evidence - Properties of evidence

that can only be associated with a general group and that can only be associated with a general group and not with a common source. e.g., blood type, paint or not with a common source. e.g., blood type, paint or dye lot, etc.dye lot, etc.

Example: from “My Cousin Vinny” (20th Century Fox)Example: from “My Cousin Vinny” (20th Century Fox)– 2 people charged with murder during a robbery at a 2 people charged with murder during a robbery at a

convenience store (“Sack-O-Suds”).convenience store (“Sack-O-Suds”).– Escaped in an older car and skidded tires while leaving.Escaped in an older car and skidded tires while leaving.– Witnesses confused but say they saw the two defendants.Witnesses confused but say they saw the two defendants.– Expert from FBI called to match tire skids with Expert from FBI called to match tire skids with

defendants car.defendants car.

Use of Class EvidenceUse of Class Evidence

Effect of “Scientific Expert” on Effect of “Scientific Expert” on JuryJuryRight to have “counter expertsRight to have “counter experts”

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Advantages of Class Physical EvidenceAdvantages of Class Physical Evidence

Provides corroboration of events based on objective Provides corroboration of events based on objective scientific datascientific data

The chances of encountering 2 indistinguishable items of The chances of encountering 2 indistinguishable items of class evidence that originated from different sources class evidence that originated from different sources are variable.are variable.

Multiple types of class evidence may lead to an extremely Multiple types of class evidence may lead to an extremely high chance that they originated from the same source.high chance that they originated from the same source.

Physical evidence has great weight in the courtroom.Physical evidence has great weight in the courtroom.

Class evidence may also serve to exonerate a person.Class evidence may also serve to exonerate a person.

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Advantages of Class Physical EvidenceAdvantages of Class Physical Evidence

Multiple types of class evidence may lead to an extremely Multiple types of class evidence may lead to an extremely high chance that they originated from the same source.high chance that they originated from the same source.

Type AB blood - 3%Type AB blood - 3%

Rh Negative - 16%Rh Negative - 16%

Left-handed - 13%Left-handed - 13%

Male - 50%Male - 50%

Probability for random match =

0.03 x 0.16 x 0.13 x 0.50 =

0.00031 or ca. 3 in 10,000

Blood TypesWorld:Type A - 42%Type B - 8%Type O - 47%Type AB - 3%

US:Type A - 39%Type B - 13%Type O - 43%Type AB - 5%

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Advantages of Class Physical EvidenceAdvantages of Class Physical Evidence

Multiple types of class evidence may lead to an extremely Multiple types of class evidence may lead to an extremely high chance that they originated from the same source.high chance that they originated from the same source.

Type AB blood = 3% And Red Haired = 3%Type AB blood = 3% And Red Haired = 3%

Rh Negative = 16%Rh Negative = 16% And Over 6’2” = 5% And Over 6’2” = 5%

Left-handed = 13%Left-handed = 13%

Male = 50%Male = 50%

Probability for random match =

0.03 x 0.16 x 0.13 x 0.50 x 0.03 x 0.05 =

0.00000047 or ca. 5 in 10 million

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Disdvantages of Class Physical Evidence

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Next Film Clip Shows Many Impt. Ideas about evidence:Next Film Clip Shows Many Impt. Ideas about evidence:Disadvantages of Class Evidence (especially for Disadvantages of Class Evidence (especially for

mass produced popular items).mass produced popular items).Expert QualificationsExpert QualificationsHow Class Evidence may be turned into individual How Class Evidence may be turned into individual

evidence.evidence.Weight accorded by juries to scientific evidenceWeight accorded by juries to scientific evidence

Voir Dire - “speaking the truth” - challenging potential Voir Dire - “speaking the truth” - challenging potential jurors and expert witnesses’ qualificationsjurors and expert witnesses’ qualifications

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How Class Evidence may be How Class Evidence may be turned into individual evidence.turned into individual evidence.

My Cousin Vinny conclusion

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Physical Evidence Individual CharacteristicsIndividual Characteristics - Properties of evidence that

can connect a sample and standard to a common source (with high probability). e.g., fingerprints, unusual wear patterns, tool marks, etc.

Body of a woman was found with a knife wound in her neck. A broken knife tip was found in the wound. The knife blade tip was compared with the knife found in the husbands pocket. Matches both in brake line and scratches.

Saferstein Fig. 3.1

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Individual Characteristics

Properties of evidence that can be attributed to a common source with an extremely high degree of certainty

Examples: bullets, knives, shattered headlight

Firearms ID

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Physical Evidence

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Physical Evidence

Lindberg Kidnapping Case

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Lindberg Kidnapping Chas. A. Lindberg - first

to fly solo across Atlantic (1927).

One of the most famous Americans in the ‘20’s and ‘30’s.

June 22, 1930, Chas. Lindberg Jr. born: Mar. 1, 1932 he was kidnapped.

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Lindberg Kidnapping Ladder Used in Abduction

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Crime-Scene Reconstruction Collaborative effort of law

enforcement personnel, medical examiners and criminalists

Was there more than one person involved?

How was the crime committed? Reconstruction supports likely

sequence of events by the observation and evaluation of physical evidence and statements made by witnesses and those involved with the incident

Reconstructions can play a vital role in aiding the jury to arrive at an appropriate verdict.

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Crime-Scene ReconstructionStep 1Step 1 - State problem - type of crime and the legal elements. - State problem - type of crime and the legal elements.

Step 2Step 2 - Collect data - - records checks and police checks, - Collect data - - records checks and police checks, interview victim, witnesses, and suspects, try to get additional interview victim, witnesses, and suspects, try to get additional witnesses and comparison samples from suspects witnesses and comparison samples from suspects

Step 3Step 3 - Form a hypothesis - look at all evidence - determine - Form a hypothesis - look at all evidence - determine motive and possible suspectsmotive and possible suspects

Step 4Step 4 - Test hypotheses - evaluate how truthful and reliable - Test hypotheses - evaluate how truthful and reliable the stories are, weigh their stories against the physical evidencethe stories are, weigh their stories against the physical evidence

Step 5Step 5 - Follow up the most promising hypotheses (theories) - Follow up the most promising hypotheses (theories)

Step 6Step 6 -- Draw conclusions - supported by court-admissible -- Draw conclusions - supported by court-admissible evidence leading to the arrest, prosecution, and conviction of evidence leading to the arrest, prosecution, and conviction of the offender.  the offender.  

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Homicide: Rape: Robbery: Burglary:

1- focus on deceased 1- focus on victim 1 - modus operandi 1 - focus on scene2 -crime scene 2 - medical reports 2 - crime scene 2 - records check3 - crime lab 3 - crime scene 3 - police records 3 - property check

4 - usual suspects

Source: adapted from Gilbert, J. (1980) Criminal Investigation. Columbus: Merrill.

PatternsPatterns -- series of similarities that indicate the same person -- series of similarities that indicate the same person or the same modus operandi is involved in different crimes.or the same modus operandi is involved in different crimes.LeadsLeads -- clues or breaks in the case that move an investigation -- clues or breaks in the case that move an investigation forward.forward.TipsTips -- provided by informants. Tips by definition involve -- provided by informants. Tips by definition involve specifics.specifics.TheoriesTheories -- beliefs that point in one direction, at the exclusion -- beliefs that point in one direction, at the exclusion of other possible directions.of other possible directions.CluesClues -- pieces of evidence that are consistent with the corpus -- pieces of evidence that are consistent with the corpus delecti or elements of the crime.delecti or elements of the crime.

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Physical Evidence

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Crime-Scene Reconstruction

Saferstein “Criminalistics”

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Kennedy AssassinationPETER JENNINGS REPORTING: THE KENNEDY ASSASSINATION: BEYOND CONSPIRACYABC News Special (Nov. 2003)

4th Amendment and Evidence Collection

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What does the 4th Amendment to the US Constitution guarantee?

When would the 4th Amendment not be applicable?