Criminal Investigation Fundamentals

The systematic and lawful process of gathering, evaluating, and documenting information and evidence to determine whether a crime occurred, identify those responsible, and support appropriate legal proceedings.

To identify the offender, locate or apprehend the offender through lawful means, and obtain evidence supporting appropriate prosecution.

The discovery or recognition of a suspected criminal offense through observation, reports, intelligence, or investigative activities.

Crime detection identifies possible criminal activity; criminal investigation systematically establishes the facts and gathers relevant evidence.

Information, interrogation, and instrumentation, commonly referred to as the three I's of investigation.

Facts or leads obtained from people, records, observations, or other sources that may help establish the circumstances of an offense.

Questioning intended to obtain relevant information, subject to constitutional rights and applicable laws governing custodial investigation.

The application of scientific methods, technical equipment, and forensic procedures to examine evidence.

To establish relevant facts objectively through lawful, reliable, and properly documented investigative procedures.

Information suggesting a possible person, location, event, item, or line of inquiry requiring verification.

A tentative explanation of an event that investigators evaluate against available and newly obtained evidence.

To reduce confirmation bias, identify inconsistencies, and avoid prematurely treating an unverified explanation as fact.

Direct evidence supports a fact without requiring an intermediate inference; circumstantial evidence supports a fact through logical inference.

Evidence consisting of statements or testimony by persons concerning facts relevant to an investigation or proceeding.

Documents or recorded materials presented to establish their contents or other legally relevant facts.

A physical item presented for examination because its characteristics or connection to events are relevant to the case.

Tangible material that may help establish the circumstances of an offense or connect people, objects, and locations.

Small or transferable material, such as fibers, glass fragments, or paint particles, that may be relevant to an investigation.

Evidence that may establish a relationship among a person, object, location, or event.

Evidence used to help infer the sequence, positions, movements, or circumstances of events under investigation.

Contact between persons, objects, or environments can result in the transfer of material, potentially leaving forensic traces.

It explains why contact-related trace materials may help establish associations during forensic investigation.

Assess immediate threats, protect life, and obtain necessary emergency assistance before proceeding with evidence-related tasks.

Secure and assess the scene, control unnecessary access, identify relevant persons, and preserve potential evidence.

Protecting the scene and potential evidence against avoidable disturbance, contamination, alteration, destruction, or loss.

To control access, protect potential evidence, and support safe and orderly investigative operations.

The primary scene is the principal location associated with the offense; a secondary scene is another location containing relevant evidence or related activity.

The introduction, transfer, alteration, or loss of material that compromises the original condition or reliability of potential evidence.

The unintended transfer of material between separate evidence items, persons, tools, or locations.

To protect safety, preserve evidence, prevent contamination, and maintain accountability for scene access.

A record identifying persons entering or leaving a secured scene, usually including relevant times and reasons for access.

To preserve an accurate account of observations and conditions before authorized activities or unavoidable events alter the scene.

An initial systematic assessment of the scene to identify hazards, evidence locations, investigative priorities, and documentation needs.

An organized examination of a scene to understand its layout, identify relevant areas, and plan appropriate documentation and processing.

To create a visual record of the scene, evidence locations, relevant relationships, and conditions at the time of documentation.

Overall, midrange, and close-up views.

To document the general setting, layout, surroundings, and spatial relationships within the scene.

To show evidence items in relation to nearby objects, landmarks, or important scene features.

To record the visible characteristics and details of specific evidence items or relevant features.

A diagram showing relevant scene features, measurements, locations, and spatial relationships.

A rough sketch is prepared during scene examination; a finished sketch is a clearer formal version based on verified scene information.

To indicate the sketch's orientation relative to geographic north.

To explain symbols, labels, abbreviations, and markings used in the diagram.

To document the collection, possession, transfer, handling, and disposition of evidence so its identity and integrity can be assessed.

The evidence identifier, persons transferring and receiving it, date and time, purpose of transfer, and relevant condition or seal information.

To reduce cross-contamination, preserve identifying characteristics, and maintain clear evidence identification.

To create a timely record of observations, actions, statements, decisions, and other facts relevant to the investigation.

An observation describes directly perceived or verified information; an inference is a conclusion drawn from evidence or observations.

Provide or obtain necessary emergency medical assistance and address immediate hazards, while preserving evidence as far as reasonably possible.

Document the inconsistency, assess the reliability of each source, seek corroboration, and consider alternative explanations without prematurely deciding which is correct.