Lesson 5
Criminal Investigation
In This Lesson
1. Investigation Fundamentals
Criminal investigation is the systematic collection and analysis of information to identify, apprehend, and assist in the prosecution of criminals.
Three I's of Investigation
Information
Data gathered from people, records, and observations that aid in solving the crime.
Instrumentation
Use of scientific tools and methods to examine evidence (forensics, criminalistics).
Interrogation/Interview
Questioning of witnesses, victims, and suspects to obtain information.
Cardinal Points of Investigation (5 W's + H)
2. Crime Scene Management
The crime scene is the actual location where a crime occurred. Proper management is critical for successful investigation.
Steps in Crime Scene Investigation
- 1
Secure and Protect the Scene
Establish perimeter; control access; preserve evidence
- 2
Conduct Preliminary Survey
Walk-through to get overall picture; identify potential evidence
- 3
Document the Scene
Photographs, sketches, notes, video
- 4
Search for Evidence
Systematic search using appropriate pattern
- 5
Collect and Preserve Evidence
Proper handling, packaging, and labeling
- 6
Release the Scene
Final survey; document release
Search Patterns
Strip/Lane Search
Back and forth in straight lines; good for large outdoor areas
Grid Search
Double strip at 90° angles; thorough but time-consuming
Spiral Search
Inward or outward spiral; good for single searcher
Wheel/Ray Search
From center outward like spokes; good for small areas
Zone/Quadrant Search
Divide into sections; good for rooms/buildings
3. Evidence Collection
Evidence is anything that tends to prove or disprove a fact in issue. Proper collection and handling is crucial for admissibility.
Types of Evidence
Physical/Real Evidence
Tangible objects: weapons, fingerprints, blood, fibers, etc.
Documentary Evidence
Written documents, records, contracts, photographs
Testimonial Evidence
Oral testimony of witnesses under oath
Circumstantial Evidence
Indirect evidence requiring inference
Chain of Custody
The chronological documentation showing the seizure, custody, control, transfer, analysis, and disposition of evidence.
- • Purpose: Prove evidence is authentic and uncontaminated
- • Documentation: Who handled it, when, where, why
- • Transfer: Each transfer must be documented
- • Storage: Secure storage with limited access
- • Integrity: Broken chain may render evidence inadmissible
Corpus Delicti
"Body of the crime" - the substance or foundation of a crime. Two elements:
- Injury or harm: Loss, damage, or injury occurred
- Criminal agency: Caused by someone's criminal act
Example: In murder, corpus delicti includes the fact of death and that it was caused by criminal act.
4. Interview & Interrogation
Interview and interrogation are techniques used to obtain information from witnesses, victims, and suspects.
Interview
- • Non-accusatory
- • With witnesses/victims
- • Information gathering
- • Conversational approach
- • Open-ended questions
- • No Miranda required
Interrogation
- • Accusatory
- • With suspects
- • Elicit confession/admission
- • Controlled environment
- • Direct questions
- • Miranda REQUIRED
Types of Questions
Confession vs. Admission
Confession
Direct acknowledgment of guilt of the crime charged
Admission
Statement of facts pertinent to the issue but not an acknowledgment of guilt
5. Case Filing & Prosecution
After investigation, the case is prepared for filing with the prosecutor's office for evaluation and possible prosecution.
Case Preparation Process
- Complete investigation report
- Compile all evidence and documentation
- Prepare sworn statements of witnesses
- Submit to prosecutor for preliminary investigation
- Prosecutor determines probable cause
- Information filed in court if probable cause exists
Investigation Report Contents
- • Synopsis: Brief summary of the case
- • Details: Full narrative of events
- • Evidence: List of all physical evidence
- • Witnesses: List with contact information
- • Suspects: Identification and description
- • Attachments: Photos, sketches, statements, lab results
Disposition of Cases
Case Filed
Probable cause found; information filed in court
Case Dismissed
Insufficient evidence; lack of probable cause
Referred
Referred to another agency or jurisdiction
Suspended
Further investigation needed; case held
NAPOLCOM Criminal Investigation Tips
- ✓Know the Three I's - Information, Instrumentation, Interview/Interrogation.
- ✓Memorize crime scene steps - from securing to releasing the scene.
- ✓Understand chain of custody - critical for evidence admissibility.
- ✓Distinguish interview vs. interrogation - know when Miranda applies.