Physical Evidence. Class characteristics: Evidence can only be associated with a group and not a...
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Transcript of Physical Evidence. Class characteristics: Evidence can only be associated with a group and not a...
![Page 1: Physical Evidence. Class characteristics: Evidence can only be associated with a group and not a unique source Individual characteristics: Evidence can.](https://reader035.fdocuments.us/reader035/viewer/2022062314/56649ee55503460f94bf58d1/html5/thumbnails/1.jpg)
Physical Evidence
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Physical Evidence
Class characteristics:Evidence can only be associated with a group and not a unique source
Individual characteristics:Evidence can be attributed to a unique source with a high degree of certainty (or even to the exclusion of all others)
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Examples of Class Characteristics
Shoes (Nike, Air Jordan, size 9)Paint (Cherry red 1967 Chevy Mustang)Fibers (Red polyester fiber, braided weave)Fingerprints (loops, whorls, arches)Toolmarks (1/4” flat blade B&D screwdriver)Firearms (.40 caliber S&W magnum pistol)Arson (accelerants)DNA (male)
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Examples of Unique Characteristics
Shoes (natural wear, bubble gum)Paint (physical match)Fibers (physical match, unique “trait”)Fingerprints (ridge detail)Toolmarks (stria markings)Firearms (stria, firing pin markings)DNA (profile)
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Scenarios
Pathology wound matches murder weapon…Glass fragments found in burglar’s coat pocket…Burglar’s tools…Poison found in suspect’s home with rare component…
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Analysis of Evidence
KnownUnknownCommon Source
e.g. the unknown XXX collected at the crime scene was compared to known XXX collected from Ms. Y and could have originated from a common source.
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Edmond Locard (1877-1966)
French investigatorBackground in medicine and law1910-started a police laboratoryFounded Institute of Criminalistics at the University of LyonsContributed to fingerprints (poroscopy)
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Locard’s Exchange Principle
Principle of cross-transferWhenever two objects come into contact there is evidence of that contact through cross-transfer…MicroscopicMacroscopic
Every contact leaves a trace!
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Physical Evidence Can…
1. Prove that a crime has been committed or establish key elements of a crime
Example Rape = victim has torn clothing, bruises, broken arm =
non-consensual
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Physical Evidence Can…
2. Link a suspect with the victim or crime scene
Example Burglary = suspect has broken glass shards in his
pants cuff that are consistent with glass shards at scene
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Physical Evidence Can…
3. Establish the identity of persons associated with a crime
Example Latent fingerprints identified through AFIS. DNA
identified through CODIS.
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Physical Evidence Can…
4. Exonerate the innocent
Example Rape = DNA preserved was compared against man
convicted of the crime = no match.
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Physical Evidence Can…
5. Corroborate the victim’s story
Example Officer involved shootings
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Physical Evidence Can…
6. Contradict information provided to investigators
Example Discredit a witness; elicit a confession
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Physical Evidence Can…
7. Be more reliable than eyewitness testimony
“[Physical Evidence] does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are. It is factual evidence. It cannot be wrong; it cannot perjure itself; it cannot be wholly absent. Only in it’s interpretation can there be error. Only human failure to find, study, and understand it can diminish its value.”
Paul Kirk, Crime Investigation, 1953
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Physical Evidence Can…
8. Be the cornerstone of a case
Police/prosecutors are expected to obtain physical evidence and rarely rely on a confession alone
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Physical Evidence Can…
9. And IS expected by a jury/the public
TV, books, media focus on physical evidence and the miracles performed (reality vs. fantasy)
The “CSI Effect”
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Lack of Physical Evidence Can…
10. Support or refute a theory
The absence of forced entry in a burglary case…