(Discussion – Evidence: Testimonial vs. Physical) Thursday September 28, 2017 (Discussion – Evidence: Testimonial vs. Physical)

Case – Accident Avoidance The Daily CSI Thursday, 9/28/17 Case – Accident Avoidance There is a man walking down a one-lane road dressed entirely in black. There are no street lights on anywhere and no moon. A car with no lights comes down the road and manages to avoid the man. How? It was daytime.

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S3 F1 F2 F3 QUIZ 3 TODAY 9/22 Next Tuesday 9/25 Next Wednesday 9/26 Assignment Currently Open Summative or Formative # Date Issued Gone Missing Day Last Day Accepted QUIZ 3 S3 9/22 Tomorrow 5:00 PM Casework – Dead Man’s Curve F1 9/25 TODAY Next Tuesday Video and Worksheet – The Value of Evidence F2 9/26 Next Wednesday Packet – Power of Evidence F3 9/27 Next Monday Next Thursday

Evidence Evidence can be divided into two categories: Testimonial - statements or the spoken word from the victim(s) or witness(es). Expert testimony – “In my opinion, the hair found at the crime scene could not have come from the accused.” Eyewitness testimony - "I saw Joe shoot Sam." Physical - also referred to as real evidence, consists of tangible articles such as hairs, fibers, latent fingerprints and biological material.

Physical Evidence It would be impossible to list all the objects that could conceivably be of importance to a crime, as almost anything can be considered “physical evidence.” The purpose of recognizing physical evidence is so that it can be collected and analyzed. It is difficult to ascertain the weight a given piece of evidence will have in a case as ultimately the weight will be decided by a jury. Although you cannot rely on a list of categories, it is useful to discuss some of the most common types of physical evidence.

Types of Physical Evidence Blood, semen, and saliva Documents Drugs Explosives Fibers Fingerprints Firearms and ammunition Glass Hair Impressions Organs and physiological fluids Paint Petroleum products Plastic bags Plastic, rubber, and other polymers Powder residues Soil and minerals Tool marks Vehicle lights Wood and other vegetative matter

The Purpose of Examining Physical Evidence The examination of physical evidence by a forensic scientist is usually undertaken for identification or comparison purposes by a forensic chemist. Identification has, as its purpose, the determination of the physical or chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit. A comparison analysis subjects a suspect specimen and a standard reference specimen to the same tests and examinations for the ultimate purpose of determining whether or not they have a common origin.

Identification The object of an identification is to determine the physical or chemical identity with as near absolute certainty as existing analytical techniques will permit. The process of identification first requires the adoption of testing procedures that give characteristic results for specific standard materials. Once these test results have been established, they may be permanently recorded and used repeatedly to prove the identity of suspect materials. Second, identification requires that the number and type of tests needed to identify a substance be sufficient to exclude all other substances.

Common Types of Identification The crime laboratory is frequently requested to identify the chemical composition of an illicit drug. It may be asked to identify gasoline in residues recovered from the debris of a fire to determine if the crime of arson was committed, or it may have to identify the nature of explosive residues— for example, dynamite or TNT. The identification of blood, semen, hair, or wood are also very common and, as a matter of routine, include a determination for species origin.

Forensic Explosive Experts Shortly after the Boston Marathon bombings, forensic explosive experts were needed on the scene.

Comparison A comparative analysis has the important role of determining whether or not a suspect specimen and a standard reference specimen have a common origin. Both the standard/reference and the suspect specimen are subject to the same tests. The forensic comparison is actually a two-step procedure. First, combinations of select properties are chosen from the suspect and the standard reference specimen for comparison. Second, once the examination has been completed, the forensic scientist must be prepared to render a conclusion with respect to the origins.

Using Physical Evidence As the number of different objects linking an individual to a crime scene increases, so does the likelihood of that individual’s involvement with the crime. Just as important, a person may be exonerated or excluded from suspicion if physical evidence collected at a crime scene is found to be different from standard reference samples collected from that subject.

SICAR (shoeprint image capture and retrieval) is a shoeprint database. Forensic Databases The Integrated Automated Fingerprint Identification System (IAFIS), a national fingerprint and criminal history system maintained by the FBI. The Combined DNA Index System (CODIS) enables federal, state, and local crime laboratories to electronically exchange and compare DNA profiles. The National Integrated Ballistics Information Network (NIBIN) allows firearm analysts to acquire, digitize, and compare markings made by a firearm on bullets and cartridge casings. The International Forensic Automotive Paint Data Query (PDQ) database contains chemical and color information pertaining to original automotive paints. SICAR (shoeprint image capture and retrieval) is a shoeprint database.