Crime Detection & Investigation
Crime Scene Procedures, Interview Techniques & Evidence Collection
Fundamentals of Investigation
Definition of Criminal Investigation
The collection of facts to accomplish the threefold aim: to identify the guilty party, to locate the guilty party, and to provide evidence of guilt.
Cardinal Points (5 W's and 1 H)
WHAT
What happened?
Nature of the crime
WHO
Who are involved?
Suspect, victim, witnesses
WHERE
Where did it happen?
Crime scene location
WHEN
When did it happen?
Date, time, duration
WHY
Why did it happen?
Motive of the crime
HOW
How was it committed?
Modus operandi
Crime Scene Investigation
Crime Scene Definition
The venue or place where the alleged crime or incident was committed, including the surrounding area and places where evidence may be found.
Types of Crime Scenes
Primary Crime Scene
Where the crime actually occurred
Secondary Crime Scene
Any other location where evidence is found
Crime Scene Search Methods
Strip/Line Method
Searchers walk in straight parallel lines across the scene.
Best for: Large outdoor areas, fields
Grid/Double Strip Method
Two strip searches at right angles to each other.
Best for: More thorough search of large areas
Spiral Method
Search moves in spiral pattern, either inward or outward.
Best for: Single searcher, smaller scenes
Zone/Quadrant Method
Area divided into zones, each searched separately.
Best for: Indoor scenes, rooms
Wheel/Radial Method
Searchers move from center outward like spokes.
Best for: Small circular scenes, single critical point
Crime Scene Procedures
Secure and Protect the Scene
Establish perimeter, prevent contamination, control access
Conduct Preliminary Survey
Walk through, observe, plan search strategy
Document the Scene
Photography, videography, sketching, note-taking
Search for Evidence
Systematic search using appropriate method
Collect and Preserve Evidence
Proper handling, packaging, marking, chain of custody
Release the Scene
Final survey, documentation, official release
Types of Evidence
Physical/Real Evidence
Tangible objects found at crime scene
Examples: weapons, fingerprints, bloodstains, clothing
Testimonial Evidence
Statements from witnesses
Examples: eyewitness accounts, expert testimony
Documentary Evidence
Written documents or records
Examples: contracts, checks, letters, receipts
Circumstantial Evidence
Indirect evidence suggesting guilt
Examples: motive, opportunity, possession of stolen goods
Corpus Delicti Evidence
Evidence that proves the body of the crime - that a crime was actually committed. Essential elements:
- Occurrence of specific injury or loss
- Criminal agency as the cause
Interview and Interrogation
Interview
- Purpose: Gather information
- Subject: Witnesses, victims
- Tone: Non-accusatory
- Setting: May be at crime scene
- Rights: Voluntary cooperation
Interrogation
- Purpose: Obtain confession/admission
- Subject: Suspects
- Tone: Accusatory
- Setting: Controlled environment
- Rights: Miranda warning required
Miranda Rights (Custodial Investigation)
Before any questioning, suspect must be informed of:
- Right to remain silent
- Anything said can be used against them
- Right to counsel (preferably of their choice)
- Right to have counsel present during questioning
- If unable to afford, counsel will be provided
Note: Must be in a language known and understood by the suspect
Modus Operandi (M.O.)
Definition
The method of operation - the particular way or manner a criminal commits a crime. It can be used to:
- Link crimes to the same perpetrator
- Predict future criminal behavior
- Narrow down suspects
Elements of Modus Operandi
Time
When the crime is committed
Place
Location and type of scene
Victim Type
Characteristics of targets
Entry Method
How access is gained
Weapon/Tools
Instruments used
Escape Method
How perpetrator leaves
Surveillance
Types of Surveillance
Stationary (Fixed)
Observing from a fixed position
Mobile (Moving)
Following the subject
Loose Tail
General location only
Close/Tight Tail
Continuous observation
Undercover Operations
Investigator assumes false identity to gather evidence. Types include:
- Roping: Investigator befriends suspect
- Buy-bust: Drug enforcement operation
- Entrapment: Legally trapping a criminal (not inducing crime)
Report Writing
Elements of a Good Police Report
- Accuracy: Facts must be correct and verified
- Completeness: All relevant information included
- Clarity: Easy to understand, no jargon
- Objectivity: No personal opinions or bias
- Timeliness: Written promptly while details are fresh
Types of Police Reports
- Spot Report: Initial/immediate report
- Progress Report: Updates during investigation
- Final Report: Complete findings and conclusions
- After Operation Report: Post-operation summary