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. 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

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)

Locard’s Exchange Principle 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!

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.

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

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…

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)

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.

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.)

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

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

Origin – Comparison to known suspects or witnesses, victims. 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

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…

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

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

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.

Impressions bsapp.com

bsapp.com

Tool Marks Match tool to scares bsapp.com

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

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.

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

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

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

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

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

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

Paint Origin Match

Documents Hand written Type or Printed Authenticity? bsapp.com

Types of Analysis Comparison Visual Microscopic Chemical bsapp.com

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

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

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

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

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

Forensic Databases IAFIS CODIS NIBIN PDQ SICAR

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

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

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

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

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