Crime Scene Investigation: Evidence Rules and Concepts

Unit 1: The Crime Scene

• A crime scene is a site or area where a crime occurred, including locations, people, places, or objects associated with criminal behavior.
• Fingerprints, photographs, physical evidence, and eyewitness testimony are types of evidence that can be collected at a crime scene.
• Evidence is anything that tends to prove or disprove the existence of a fact, and has three basic functions in court:
  • To prove or disprove a crime
  • To support or undermine other evidence
  • To help determine an appropriate sentence
• There are two broad types of evidence: direct and indirect (or circumstantial).

Evidence Collection

• Direct evidence proves a fact without an inference or presumption, and conclusively establishes that fact.
• When collecting latent prints, use lifting tape to develop the prints, and follow these steps:
  • Smooth out the lifting tape to remove air bubbles
  • Slowly lift the tape from the same end where you started rolling it
  • Carefully place the tape on the fingerprint card
  • Record the date, case number, location, and other required information on the back of the card
• Elimination prints are used to distinguish between prints belonging to victims, witnesses, or suspects.

Firearms Evidence

• When recovering a firearm or ammunition at a crime scene, follow agency policies and procedures for handling evidence, and use PPE to avoid contaminating the evidence.
• When collecting drug paraphernalia, package sharp objects in puncture-proof packages and label them with a warning.

Hazardous Substances

• Fentanyl and carfentanil are hazardous substances that can be absorbed through mucous membranes.
• When encountering these substances, follow agency policies and procedures for field-testing, collecting, packaging, and transporting.
• Use PPE, such as gloves, masks, and eye protection, and conduct field-testing in an open environment.
• Signs of exposure to fentanyl or carfentanil include disorientation, difficulty speaking or walking, slowed pulse, nausea, and respiratory arrest.

Modus Operandi (MO)

• MO is a latin term that refers to a person's habits or method of operation.
• When comparing MO, consider the following factors:
  • Was the crime well-planned or impulsive?
  • Were tools used, and what kind?
  • What property was stolen, and how much?
  • What damage was done, and why?
  • Was the suspect motivated by profit, revenge, or opportunity?

Unit 2: Follow-Up Investigation

Gathering Information on a Known Suspect

• When searching for a known suspect or wanted person, gather information from additional sources, such as:
  • Juvenile information through criminal justice agencies
  • School resource officers
  • Initial incident report, victim and witness statements
• Review information from the initial incident report and conduct criminal justice database searches to compile an accurate physical description of the suspect.

Searching for a Known Suspect or Wanted Person

• Conduct criminal justice database searches on DAVID and FCIC/NCIC to obtain the suspect's full name, race, gender, and date of birth.
• Use this information to determine the suspect's likely location, including their residence, place of employment, or public or private locations they regularly visit.
• Remember to obtain a warrant when necessary.

Maintaining Contact with Dispatch

• Maintain constant contact with dispatch when physically searching for a wanted person, updating your location and status to maintain a high level of officer safety.
• This is critical when searching for an armed suspect.
• If unable to arrest the wanted person, initiate a BOLO for the suspect and pass any suspect information to the next shift and the appropriate department within your agency.