Crime Scene Investigation: Evidence Rules

The Crime Scene

• A crime scene is the site or sites where a crime occurred, including an area or areas that contain evidence from the crime committed.
• A crime scene can be a location, a person, a place, or an object associated with criminal behaviors.
• Types of evidence at a crime scene include fingerprints, photographs, physical evidence, and eyewitness testimony.

Function of Evidence

• Evidence is anything that tends to prove or disprove the existence of a fact.
• Evidence has three basic functions when offered in court:
  • To prove or disprove a crime
  • To support or undermine other evidence
  • To help determine an appropriate sentence

Types of Evidence

• There are two broad types of evidence: direct and indirect (or circumstantial).
• Direct evidence proves a fact without an inference or presumption and which, if true in itself, conclusively establishes that fact.
• Recognizing threats to the evidence will determine the appropriate method of protection.
• Protecting evidence from weather elements such as rain, hail, lightning, or wind is crucial in outdoor crime scenes.

Securing the Crime Scene

• Determine if the location is public or private property.
• Public property is for the use and enjoyment of the public and is open to the public.
• Private property belongs to an individual and is not open to the public.
• An officer has permission to enter private property based on exigent circumstances to conduct a sweep for potential suspects, to provide first aid, or if there is an indication that evidence will be lost, destroyed, or removed prior to obtaining a search warrant or consent to search.

Documenting the Crime Scene

• Photographing the crime scene is the first step in documenting the scene.
• Photographing allows people who were not present at the original scene to gather information and visualize how the crime scene looked on the day of response.
• Photographs or sketches also help victims and witnesses refresh their memory as time goes by.
• Crime scene photography moves from general to specific, taking overall, midrange, and then close-up photographs.
• Close-up shots show the details of a specific item of evidence and must include a scale or identifier.

Gather Information on an Unknown Suspect

• Modus operandi (MO) refers to how someone does something, usually repetitive in nature.
• People are creatures of habit, and MO may show up in criminal activity.
• A person's MO may include repeatedly using the same method of entry when committing burglaries, stealing similar types of items, choosing victims who share similar characteristics, or committing their crimes with similar locations, days, and times.
• Developing an unknown suspect takes a team approach, often with the help of an outside agency or an analyst.

Crime Patterns

• Develop potential suspects by locating reports of crimes similar to the crime being investigated.
• Review reports for similarities, such as type of crime scene, time, and day of occurrences, methods and points of entry and exit, and evidence found at the scenes.

Preparing for Testimony

• Review reports created, as well as the complete case file, including all other reports, photos, videos, evidence, and the chain of custody.
• Discuss the case with the state attorney's office to identify and understand areas of weakness relevant to testimony and to clarify any concerns the state attorney may have.
• Identify witness information and give it to the state attorney's office.
• Be prepared to answer questions on all relevant facts and to testify from memory.
• Assume that the defense attorney knows everything you know.
• Always prepare for testimony the same way, reviewing all case documentation, discussing the case with the prosecutor, and following the guidelines for giving an effective testimony.

Witness Interviews and Statements

• Separating witnesses and victims during a crisis may be necessary to ensure accurate statements, but use judgment and empathy when assessing the need for separation.
• Remove suspects or other witnesses who attempt to influence or intimidate others from giving false information.
• Maintain visual contact with victims, witnesses, and suspects for safety reasons.
• If an interviewee is suffering from physical or mental trauma, consider interviewing them later when they have recovered.

Injured People and First Aid

• Responding officers may need to provide first aid to injured people at the scene.
• Consider asking direct, fundamental questions about the injury while providing emergency first aid, such as:
  • Who hit you?
  • What did the suspect use to hit you?
  • Where were you hit?
  • Where were you standing when you were hit?
  • When were you hit?
  • How were you hit?
  • Why were you hit?

Documenting Evidence

• Document photographs and sketches of the crime scene or person by writing the following information on a piece of paper or whiteboard:
  • Case number
  • Location
  • Date and time
  • Officer's name
• Include this information in the report, and be able to testify that the photographs or sketch are true and accurate representations of the crime scene or person.

Crime Scene Sketching

• Sketch the crime scene after photographing the scene and before beginning detailed work.
• Sketches supplement field notes and photographs, and aid in the reconstruction, explanation, and permanent recording of an incident.
• Use sketches to document where evidence was recovered and to correlate testimony during interviews with witnesses, victims, and suspects.

Latent Fingerprint Collection

• Use a basic latent fingerprint kit that includes gloves, black and light gray powder, a brush, lifting tape, and fingerprint cards.
• Follow guidelines when dusting for and lifting latent prints, including:
  • Wearing gloves to avoid contaminating the area with your own fingerprints and DNA.
  • Holding a flashlight at an angle to look for obvious signs of a latent print.
  • Using a brush and powder sparingly to avoid smudging or smearing existing latent prints.

Relationships and Information Sources

• Recognize the importance of building relationships with sources of information, such as field contacts and confidential sources.
• Verify field contact information using known case facts or public records, and document the information in field notes.
• Differentiate between field contacts and confidential sources, and understand the roles of each in providing information.

Testifying in Court

• Techniques for testifying in court include:
  • Pausing and staying calm when asked questions.
  • Asking the attorney to repeat questions one at a time and taking time to consider each question.
  • Staying alert and controlling your ego to avoid being led into giving answers that favor the defense.
  • Politely correcting the defense attorney if they mispronounce your name, title, or rank.

Learn about the rules and concepts of evidence collection at a crime scene and how to apply them to support a successful prosecution. Covers types of evidence to look for.