Unit one forensics science

Crime Scene

Any location where a crime has occurred or where evidence related to a crime can be found.

Primary Crime Scene

The main location where the crime actually took place.

Secondary Crime Scene

Any additional location that contains evidence related to the crime but is not the primary location.

Macroscopic Crime Scene

The large-scale view of a crime scene, including the overall layout and visible evidence.

Microscopic Crime Scene

The small-scale evidence not visible to the naked eye, such as hair, fibers, or DNA.

Locard’s Exchange Principle

The principle that whenever two objects come into contact, there is a transfer of material between them.

Corpus Delicti

The facts and evidence proving that a crime has been committed.

Modus Operandi (MO)

The specific method or pattern of behavior a criminal uses to commit a crime.

Evidence

Any material item that can be used to establish facts in a criminal investigation.

Evidence Log

A detailed record listing all evidence collected at a crime scene.

Chain of Custody

A written record that tracks who collected, handled, transferred, and stored evidence from the crime scene to court.

Bindle

A folded paper packet used to collect and store trace evidence such as hair or fibers.

Kapak Plastic Bags

Special evidence bags used for drugs or chemicals because substances can diffuse through regular plastic bags.

DNA Preservation

Blood evidence must be dried and stored in breathable packaging (like paper) to prevent mold and DNA degradation.

Sealing Evidence

Evidence packages must be sealed with tape, labeled, dated, and initialed to maintain integrity.

Wide-Angle Photograph

Captures the entire crime scene and its surroundings.

Mid-Range Photograph

Shows the relationship between evidence and its location in the scene.

Close-Up Photograph

Focuses on specific pieces of evidence, often taken with a scale.

Crime Scene Notes

Written documentation that includes the date, time, location, description of the scene, evidence collected, and actions taken by investigators.

Crime Scene Sketch

A drawn representation of the crime scene showing measurements and spatial relationships.

Baseline Method

Measurements are taken from a single reference line to locate evidence.

Triangulation Method

Evidence is located by measuring from two fixed reference points.

Polar Coordinates Method

Evidence location is determined using a distance and angle from a fixed reference point.

Parallel/Strip Search

Investigators move in straight, parallel lines; useful for large outdoor scenes.

Grid/Double-Line Search

A more thorough version of the strip search, conducted in two directions.

Zone or Quadrant Search

The scene is divided into sections and searched individually; ideal for buildings.

Spiral Search

Investigators move in a circular pattern; used when there is only one investigator.

Wheel or Ray Method

Searches radiate out from a central point; useful for small scenes.

Link Method

Focuses on relationships between evidence, locations, and people.

IAFIS

Integrated Automated Fingerprint Identification System, an FBI database used to store and compare fingerprints.

CODIS

Combined DNA Index System, a national database that stores DNA profiles to assist in criminal investigations.

Eyewitness Testimony

A statement given by someone who witnessed a crime; it is often unreliable due to memory errors, stress, and bias.

Memory Reliability

Human memory is reconstructive, not a perfect recording; can change over time and is influenced by stress.

Stress and Weapon Focus

High-stress situations impair perception and recall; witnesses often focus on the weapon rather than the suspect.

Suggestion and Bias

Eyewitnesses can be influenced unintentionally by leading questions or pressure to choose a suspect, contributing to wrongful convictions.