Investigative techniques (law enforcement)

Investigative techniques are methods law-enforcement agencies use to gather and analyze evidence, identify suspects, and reconstruct events in criminal cases.

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Crime scene investigation: The systematic documentation and examination of a location connected to a suspected crime. It preserves physical traces and records a scene before evidence is collected.
Physical evidence: Tangible material that may help establish facts in an investigation or legal proceeding. Many investigative methods begin by locating, preserving, and interpreting physical traces.
DNA profiling: The analysis of selected DNA variations to distinguish individuals or assess biological relationships. It can compare biological traces with reference samples or searchable databases.
Eyewitness identification: A witness's recognition or selection of a person as someone seen during an event. Unlike laboratory comparisons, identification depends on human memory and can be affected by procedure.
Wrongful conviction: A conviction of a person who did not commit the crime or was not legally responsible for it. Faulty identifications, contaminated evidence, and misleading conclusions can contribute to wrongful convictions.
Forensic science: The application of scientific methods to questions arising in legal proceedings. Laboratory analysis can identify or compare traces recovered during investigations.
Locard's exchange principle: The forensic principle that contact between entities can result in material transfer. It explains why contact may leave trace evidence, though transfer alone does not prove when or how it occurred.
Fingerprint analysis: The examination and comparison of friction-ridge patterns from fingers and palms. Latent prints can associate a person with an object or location, subject to interpretation limits.
Confession: A statement in which a person acknowledges involvement in a crime. A confession is testimonial evidence, not independent confirmation that its account is accurate.
Exclusionary rule: A legal doctrine that bars certain unlawfully obtained evidence from being used in court. It can limit the courtroom use of evidence gathered through prohibited investigative conduct.