Types of Physical Evidence

Physical Evidence

• Physical evidence can be classified into three categories: fruits of a crime, instrumentalities of a crime, and contraband.
• Fruits of a crime are the objects obtained by the defendant as a result of committing the crime.
• Instrumentalities are the items used by the defendant to commit the crime.
• Contraband is any property that is illegal for a person to possess based on statute, ordinance, or rule.

Admissibility of Evidence

• Admissibility of evidence refers to the legal requirements that must be met before a jury can see or hear about the evidence.
• The evidence must be deemed relevant and real.
• The evidence must be obtained legally and preserved properly.
• The evidence cannot be unfairly prejudicial, confusing, or based on hearsay.
• The fruit of the poisonous tree doctrine holds that the court may exclude evidence from trial if the officer obtained it illegally.

Responding to a Crime Scene

• When responding to a crime scene, the officer's first priority is to secure, protect, and preserve the scene to avoid contaminating any evidence.
• The officer's second priority is to search for, identify, document, collect, and maintain the physical evidence.
• The officer should consider key questions to help assess the situation adequately, such as:
  • What is the location?
  • Are any weapons involved?
  • Has the complainant indicated the suspect's location?
  • How many individuals are involved?
  • How many officers are necessary to safely contain or control the situation?
  • Do you need additional services?
  • Do you need special equipment?
  • Are any special concerns or dangers associated with the call?

Collecting Latent Prints

• To collect latent prints, the officer should use lifting tape and follow a specific procedure to avoid damaging the print.
• The officer should record the date, case number, location, and other relevant information on the back of the fingerprint print card.

Elimination Prints

• Elimination prints allow fingerprint analysts to distinguish between prints belonging to victims, witnesses, or suspects.
• The officer should take fingerprints from anyone who may have been at the crime scene to eliminate their prints from the pool of suspects.

Firearms Evidence

• When recovering a firearm or ammunition at a crime scene, the officer should follow agency policies and procedures for handling such evidence.
• The officer should apply PPE to avoid contaminating the firearm or ammunition with their fingerprints and DNA.

Pretrial Meeting

• Before a pretrial meeting, the officer should thoroughly review all available case documentation.
• The officer should discuss the case with the appropriate agency personnel, such as their supervisor, watch commander, or crime scene and evidence personnel.
• The officer should be prepared to discuss who, what, when, where, how, and why facts of the case, as well as all evidence and other relevant information.

Cross-Examination Tactics

• During a criminal trial, attorneys may use various tactics to discredit, misrepresent, or confuse the officer.
• The officer should be aware of these tactics and go into court with basic techniques to overcome them.
• The officer should convey professionalism, knowledge, and confidence and give firm, decisive answers.
• The officer should not be confrontational or argumentative, and should remain calm and composed under cross-examination.