2 Types of Evidence2 types existTestimonialPhysical
3 Testimonial Evidence Statement made under oath Known as direct evidenceAKA Prima Facie evidence
4 Reliability of Eyewitnesses Factors that can help or hurt your caseNature of the offense and the situation in which the crime is observedCharacteristics of the witnessManner in which the information is retrievedWitness’s prior relationship with the accusedLength of time between the offense and the identificationAny prior identification or failure to identify the defendantAny prior identification of a person other than the defendant by the eyewitness
5 EyewitnessA police composite may be developed from the witness by forensic artist or a computer programAs a result of the influences in eyewitness memory, physical evidence becomes critical.
6 Physical EvidenceImpossible to list ALL objects that can be found at a crime sceneRemember, physical evidence can be ANYTHING
7 Common Types of Physical Evidence BloodSemenSalivaDocumentsDrugsExplosivesFibersFingerprintsFirearms and ammunitionSoil and mineralsVehicle lightsGlassHairImpressionOrgansPetroleum productsPlastic bagsPlastic, rubber, and other polymersPowder residueSerial numbersWood and other vegetative matter
8 Types of Physical Evidence 5 types existTransientPatternConditionalTransferAssociative
9 Transient EvidenceIs temporary evidence; can be changed or lost; usually observed by the first officer at the sceneExamplesOdor- perfume, gas, urine, cigaretteTemperature- surroundings, coffee, water, dead bodyImprints and indentations- footprints, teeth marks, tire marksMarkings
10 Pattern EvidenceProduced by direct contact between a person and an object or between two objectsExamplesBlood spatterGlass fractureFire burn patternTire marksGun powder residueBody positionTool marksFurniture positionProjectile trajectory
11 Conditional Evidence Produced by a specific event or action Examples Light- lighting conditionsSmoke- color, direction of travel, density, odorFire- color and direction, speed of spread, temperature and condition of fireLocation- injuries or wounds, bloodstain, victim’s vehicle, weapons, broken glassVehicles- doors locked or unlocked, windows opened or closedBody- position, types of wounds; rigor, livor, and algor mortisScene- condition of furniture, doors and windows, signs of struggle
12 Transfer EvidenceProduced by contact between person(s) or object(s), or between person(s) and person(s)ExamplesFingerprintsHairFibers
13 Associative EvidenceItems that may associate a victim or suspect with a sceneExamplesSuspect has victim’s credit card or watch
15 Value of Physical Evidence Generally more reliable than testimonialCan prove that a crime has been committedCan corroborate or refute testimonyCan link a suspect with a victim or with a crime sceneCan establish the identity of persons associated with the crimeCan allow reconstruction of events of a crime
16 Forensic Investigations Includes some or all of the seven major activitiesRecognition- ability to distinguish important evidence from unrelated materialPattern recognitionPhysical property observationInformation analysisField testingPreservation- collection and proper preservation of evidence
17 Forensic Investigations Identification- use of scientific testingPhysical propertiesChemical propertiesMorphological propertiesBiological propertiesComparison- 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
18 Forensic Investigations Individualization- demonstrating that the sample is unique, even among members of the same classInterpretation- gives meaning to all the informationReconstruction- reconstructs the events of the caseInductive and deductive logicStatistical dataPattern analysisResults of laboratory analysis
19 Common Types of Identification Crime labs may be requested to identify the followingChemical composition of illicit drugsGasoline in residuesNature of explosive residuesBlood, semen, hair, or woodBlood has to be identified as human vs. other animal
20 Classifying Characteristics 2 types of characteristicsIndividualEvidence that can be associated with an extremely high degree of probabilityExample- each gun makes a different impression on the bullet when firedClassEvidence associated only with a groupExample- blood types
21 Class vs IndividualThese fibers are class evidence; there is no way to determine if they came from this garmentThe large piece of glass fits exactly to the bottle; it is individual evidence
22 Role of ProbabilityImportant in ascertaining the origins of 2 or more specimensIt is the frequency of occurrence of an event
23 Example- BadSuppose a crime took place in which the suspect left blood behind. The forensic scientist determined that the suspect has type A blood. Any person brought in and whose blood type was also A cannot be arrested on that ground because over ¼ of the population have that blood type.
24 Example- GoodSuppose a crime took place in which the suspect left saliva behind. The forensic scientist did a DNA analysis of the saliva and came up with a match to the actual suspect.