Forensics Unit 1.3 Notes

Alternative transcript:

evidence found at a crime scene. Chemical test can reveal gunshot residue (GSR) on the hands, face, or clothing of a victim or suspect to indicate how close a person was to a fired gun. Rifling (grooves) in a barrel causes distinctive grooves, indentations, and scratches upon fired bullets, which can be matched to the weapon that fired them. Police are able to search the Integrated Ballistics Identification System (IBS) database to compare marking from ballistic evidence. Dust and Dirt Dust, dirt, or sand evidence can reveal where a person has traveled and may be picked up at a crime scene or left behind. Investigators examine the samples for criminal composition, pollen, plant material, and organic matter to find links to a specific crime-scene. 2 Fingerprint (Latents) Investigators identify unique ridge characteristics in a fingerprint that can be used to identify the suspect or victim. A.F.I.S (Automated Fingerprint Identification System) is a database used by investigators at a local, state, and national levels to search for matches to fingerprints found at a crime. Fracture matches When an object is broken, torn, or cut two unique edges are formed, which are referred to as fracture lines. These edges can be compared by the naked eye or with microscopes to see if they fit together, which indicated that they may have been part of the same object at one time. Investigators may compare the edges on pieces of tape, glass fragments, paint chips, pieces of a car from an accident, paper bag, ect, to find possible matches. Impression Evidence Shoeprints and Tire Tracks Impression evidence can be photographed, lifted with tape, or cast with plaster to compare to a suspect's shoes or tires. Investigators identify patterns for identifying brands and other physical features to provide leads in the case. SHoes and tires will also show wear patterns after being used for a period of time as well as other features (Scratches, nicks, and cuts) that can be used to match evidence to specific items. 3 Tool Marks Tiny nicks and chips form on the edge of a tool as it is used, which can be used to identify matches between evidence and suspects. Tools may also pick up traces of blood or other substances that can be tested or have fingerprints that can be lifted. Questioned Documents Examiners will analyze a ransom note or other documents to find clues to link it to a crime scene or a specific suspect. They will analyze the type of paper used, printing method, handwriting style, and type of ink. Other unique features, such as watermarks or indentations made as someone wrote on a page in a notebook, may provide useful clues. Serology Blood, semen, saliva, sweat, and urine can be analyzed to give investigators information about the crime as well as it's victim or suspect. Chemicals and ultraviolet light can be used atb a crime scene to find body fluid evidence. Areas with potential evidence are swabbed, bagged and collected in vials, which are air tight and have a low risk of cross contamination. DNA Investigators can extract DNA from almost any tissue, including hair, fingernails, bones, teeth and body fluids. The DNA is used to create a profile that can be compared to profiles from suspects or victims CODIS (Combined DNA Index System) is a database maintained by the FBI that is used to find matches to unknown DNA samples from a crime scene. 4 Skeletal Remains (Anthropology) Forensic anthropologist analyze skeletal remains to determine four characteristics for a victim (age, sex, race, and stature(height/build)): Sex: Determined by examining the pelvis, humerus, and femur Age and stature: Determined by analyzing the development of the teeth, bone growth, and the length of specific bones, such as the femur. ★ Race: Determined by analyzing the skull for characteristics that are common among people of different races. DNA samples can be collected from bone, teeth, and hair to provide clues to a person's identity. Scientist may also be able to gain clues as to a person's past, recent injuries, or the cause of death based on bone fractures and other signs of trauma. Hair and Fibers Hair and fibers may be transferred from the suspect or the suspect's clothes to the victims' and vice versa. For example, a suspect may pick up carpet fibers on his shoes or leave hairs behind at a crime scene. Hairs can be examined to identify their origin, such as human or animal hairs with roots intact can be tested for DNA. 5 Fibers are used to make clothing, carpeting, furniture, beds, and blankets. They may be natural fibers from plants, animals, or synthetic fibers that are man made.