Crime Scene Basics

1. Crime Scene Basics General Science 1 Spring ‘08 Adapted from T. Trimpe 2006 http://sciencespot.net

2. Crime Scene Vocabulary • Crime Scene: Any physical location in which a crime has occurred or is suspected of having occurred. • Primary Crime Scene – The original location of a crime or accident. • Secondary Crime Scene – An alternate location, such as where additional evidence may be found. • Suspect: Person thought to be capable of committing a crime. • Accomplice: Second person associated with committing a crime. • Alibi: Statement of where a suspect was at the time of a crime.

3. Crime Scene Vocabulary • Chain of custody- the documented and unbroken transfer of evidence • Crime-scene investigation- a multidisciplinary approach in which scientific and legal professionals work together to solve a crime • First Responder- the first police officer to arrive at a crime scene

4. Locard’s Exchange Principle • When a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur. • The intensity, duration, and nature of the materials in contact determine the extent of the transfer. • Fistfight vs. brushing up against someone

5. Evidence used to resolve a crime can be split into 2 areas: testimonial evidence and physical evidence. • The testimonial evidence would be any witnessed accounts of an incident or crime. • The physical evidence would refer to any material items that would be present on the crime scene or the victims. These items would be presented in a crime investigation to prove or disprove the facts of the issue. • Examples include DNA, the body itself, the weapon used, pieces of carpet, blood and other body fluids, fingerprints, or casts of footprints or tire prints. • Trace evidence refers evidence that is found at a crime scene in small but measurable amounts. Source: http://www3.sc.maricopa.edu/ajs/crime_scene_technician.htm

6. What evidence can be found at a crime scene? Brainstorm with your group to come up with a list of evidence you might find at a crime scene and how it could be used by investigators. What will evidence collected at a scene do for the investigation? • May prove that a crime has been committed • Establish any key elements of a crime • Link a suspect with a crime scene or a victim • Establish the identity of a victim or suspect • Corroborate verbal witness testimony • Exonerate the innocent. • Give detectives leads to work with in the case Source: http://www3.sc.maricopa.edu/ajs/crime_scene_technician.htm

7. Investigating the Evidence Forensic Science disciplines at the Illinois State Police Crime Labs Drug Chemistry – Determines the presence of controlled substances and the identification of marijuana Trace Chemistry - Identification and comparison of materials from fires, explosions, paints, and glass. Microscopy - Identification and comparison of hairs, fibers, woods, soils, building materials, insulation and a broad group of materials referred to as "particulate unknowns.” Biology/DNA - Presence and comparison of body fluids and dried stains such as blood, semen, and saliva. Toxicology – Determines the presence of drugs and poisons in tissue, blood, urine and other body fluids. Latent Prints - Identification and comparison of hidden impressions from sources like fingers, palms, feet, shoes, ears, lips or the tread on vehicle tires. Firearms & Toolmarks - Examination and comparison of fired bullets, discharged cartridges, guns, gunpowder patterns, and marks left by erased serial numbers in metal or by burglary tools like a pry bar or screwdriver. Questioned Documents - Side by side comparisons of questioned handwriting and hand printing, ink, paper, writing instruments, printers, photocopiers, additions, eradications, obliterations, watermarks, and impressions. Source: http://www.isp.state.il.us/forensics/

8. Crime Scene Protocol • Interview - The first step in processing a crime scene begins with interview of the first officer at the scene or the victim to determine what allegedly happened, what crime took place, and how was the crime committed. This information may not be factual information but it will give the investigators a place to start. • Examine - The second step in the investigating a crime scene, which will help identify possible items of evidentiary nature, identify point of entry and point of exit, and getting the general layout of the crime scene. • Photograph - The third step in the protocol, which involves creating a pictorial record of the scene and record items of possible evidence. Crime scene photographs are generally taken in two categories, overall views and items of evidence. • Sketch - The fourth step in the protocol involves drawing a rough sketch to demonstrate the layout of the crime scene or to identify the exact position of the deceased victim or evidence within the crime scene. A crime scene sketch may not be completed on every case, however some form of sketching usually occurs in most cases, i.e., on a fingerprint lift card to identify exactly where the latent was recovered. • Process – This is the last step in the protocol. The crime scene technician will process the crime scene for evidence, both physical and testimonial evidence. It is the crime scene technicians responsibility to identify, evaluate and collect physical evidence from the crime scene for further analysis by a crime laboratory. Source: http://www.feinc.net/cs-proc.htm