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Types of Physical Evidence Chapter 3 Notes

Types of Physical Evidence Chapter 3 Notes. bsapp.com. I CAN Skills for the Physical Evidence Unit. I Can review the common types of physical evidence at crime scenes. I Can explain the difference between the identification and comparison of physical evidence.

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Types of Physical Evidence Chapter 3 Notes

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  1. Types of Physical EvidenceChapter 3 Notes bsapp.com

  2. I CAN Skills for the Physical Evidence Unit • I Can review the common types of physical evidence at crime scenes. • I Can explain the difference between the identification and comparison of physical evidence. • I can define and contrast individual and class characteristic of physical evidence. • I can explain the value of class evidence as it relates to a crime case. • I can list and explain the function of national databases available to forensic scientists. Video

  3. Edmond Locard (1877-1966) French investigator Background in medicine and law 1910-started a police laboratory Founded Institute of Criminalistics at the University of Lyons Contributed to fingerprints (poroscopy)

  4. Locard’s ExchangePrinciple • Principle of cross-transfer • Whenever two objects come into contact there is evidence of that contact through cross-transfer… • Microscopic • Macroscopic • Every contact leaves a trace!

  5. 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 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 3. Establish the identity of persons associated with a crime Example : Latent fingerprints identified through AFIS. DNA identified through CODIS.

  6. PHYSICAL EVIDENCE CAN: • Exonerate the innocent. Example : Rape = DNA preserved was compared against man convicted of the crime = no match. • Corroborate the victim’s story. Example: Officer involved shootings during arresting a suspect. • Contradict information provided to investigators. Example : Discredit a witness; elicit a confession 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

  7. 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. 9. And IS expected by a jury/the public. TV, books, media focus on physical evidence and the miracles performed (reality vs. fantasy) 10. Support or refute a theory. The absence of forced entry in a burglary case…

  8. Class and Individual Characteristics of 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)

  9. Examples of Class Characteristics • Shoes (Tennis shoe; Nike) • Paint (Cherry red car paint) • Fibers ( polyester fiber, braided weave) • Fingerprints (loops, whorls, arches) • Toolmarks (knife scratch, screwdriver marks) • Firearms (.40 caliber slug) • Arson (accelerants) • DNA (male…remember the sex genes; XY) or the female XX genes in a genotype of the blood.

  10. Individual Characteristics of Evidence at a Crime Scene • Shoes (Nike Lunar Vapor 8 Tour Men's Tennis Shoe, size 7) • Paint (physical match with a identified car) • Fibers (physical match, unique “trait” of a particular garmet) • Fingerprints (ridge detail enough for database comparison) • Toolmarks (unique stria markings) • Firearms (stria matching a test fired bullet, firing pin markings) • DNA (profile that matches the suspect identically.)

  11. Value of Class Physical Evidence • The value of class evidence lies in its ability to corroborate events in a manner that is nearly free of human error and bias. Class evidence is not as specific as individual, but can produce results that exclude a suspect. • As the number of different objects links an individual to a crime scene. • A person may be excluded or exonerated from suspicion if physics evidence collected at a crime scene is found to be different from the standard samples taken from the individual. DNA

  12. Common Types of Physical EvidenceBiological • Human / animal origins • Blood • Saliva • Semen • DNA hair profile. • Physiological fluids • Fingerprints • Hair • Tissues • Bodies

  13. Type of Analysis of Blood, Semen,Saliva, Organs, & other Physiological Fluids • Origin – Comparison to known suspects or witnesses, victims. • DNA- Lab analysis to prove who was there and who was not. • Condition- samples must be in good enough condition to be analyzed. Watch for contamination with external chemicals / materials. bsapp.com

  14. Examples of Physical Evidence being Individual and Proof • 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…

  15. Fingerprints • Mainstay of Forensics • Who is on file? bsapp.com

  16. Hair • What type? • How removed? • Match to a person • DNA bsapp.com

  17. Impression Crime Scene Evidence • Tire Markings – types and sizes of tires, weights • Shoe prints - tread, depth, weight, forces • Depressions in soft soils- Remnants of actions and activities of numerous people or animals. • All types of tracks- machines, animals, humans. • Material Impressions • Fabric- gloves, clothing, packs and cases. • Tool marks- hand tools, machine parts, bullet riffling. • Bite marks- human, dog, lions and tigers and bears! • Impact impressions – car lisence plates, bumper shapes. • Soils, mud, waste residue.

  18. Impressions bsapp.com

  19. bsapp.com

  20. Tool Marks • Match tool to scares bsapp.com

  21. Soils, Minerals, Wood, and Other Vegetative Matter. • Location • Link suspect • Trace Evidence bsapp.com

  22. MANUFACTURED ITEMS • These are man made items that are very commonly found at the scene of a crime. • Weapons of all kinds: Firearms, ammo, knives, swords, machetes, chainsaws, ropes, explosives, bombs or components like blasting caps. • Polymers, plastic bags, paint, glass, fibers, petroleum products, vehicle headlights. • Drugs, chemicals, • Documents or computer programs.

  23. Firearms and Ammunition • Circumstances of discharge • Link to suspect • Link to weapon • Link to victim bsapp.com

  24. Powder Residue • Evidence of shooting • Circumstances of shooting • Type of weapon bsapp.com

  25. Drugs • Type of Drug? • Strength? • Origin? • Legal? bsapp.com

  26. Explosives & Propellants • Link to suspect or victim by person, place or thing. • Origin; military, civilian? bsapp.com

  27. Fibers • Link suspect to a location or victim by direct comparison • Origin? Type? bsapp.com

  28. Glass • How broken? • Link a suspect to a crime scene • Fingerprints • Blood; type. bsapp.com

  29. Paint • Origin • Match

  30. Documents • Hand written • Type or Printed • Authenticity? bsapp.com

  31. Types of Analysis • Comparison • Visual • Microscopic • Chemical bsapp.com

  32. bsapp.com Comparison Most types of evidence require a control with which to be compared http://www.fbi.gov/about-us/cjis/fingerprints_biometrics/iafis/iafis

  33. IDENTIFICATION • Identification has as its purpose the determination of the physical or chemical identity of a substance with near certainty in accuracy. • Identify the substance and rule out any closely related substance. Ex. Drugs. Make sure it is cocaine and not PCP. • Standards within databases are compared by computer analysis to help speed things up. • http://webbook.nist.gov/chemistry/ • http://www.fbi.gov/about-us/cjis/fingerprints_biometrics/iafis/iafis

  34. Visual Analysis Evidence utilized through unaided observation bsapp.com

  35. Microscopic Analysis Evidence observed with the use of some type of microscope bsapp.com

  36. Chemical Analysis Evidence subjected to any type of chemical procedure bsapp.com

  37. Forensic Databases • IAFIS • CODIS • NIBIN • PDQ • SICAR

  38. IAFIS DATABASE • The INTEGRATED AUTOMATED FINGERPRINT IDENTIFICATION SYSTEM. • Started by FBI in 1999 • 50 million people’s prints.

  39. CODIS • COMBINED DNA INDEX SYSTEM • Created by FBI in 1998 • Compares the DNA of known criminals and crime scene evidence. • 7 million profiles

  40. NIBIN • NATIONAL INTEGRATED BALLISTICS INFORMATION NETWORK. • Made by Bureau of Alcohol, Tobacco, Firearms and Explosives. • 900,000 samples.

  41. PDQ • INTERNATIONAL FORENSIC AUTOMOTIVE PAINT DATA QUERY database • 50000 paint samples analyzed for standards.

  42. SICAR • SHOEPRINT IMAGE CAPTURE AND RETIEVAL DATABASE • 17000 different patterns scanned so far. • Allows for comparison of foot prints at scene to known standards.

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