Module 8.3: Tools of Investigation (The 3 I's)

I. Information: The Lifeblood of Investigation

Definition: Information is the raw material of an investigation. It consists of all the knowledge, data, and facts gathered from various sources that are relevant to the case. Without information, an investigation cannot even begin.

A. The Goal of Information Gathering

The ultimate goal is to transform raw information into intelligence—information that has been analyzed and evaluated for its accuracy and relevance. This intelligence then guides the investigator's actions and decisions.

B. Sources of Information

A good investigator knows where to look for information. Key sources include:

People (Human Sources):
- Victims: Provide the initial report and details of the crime.
- Witnesses: Persons who saw or heard something relevant to the crime.
- Informants (Confidential Informants): Individuals who provide information to the police on an ongoing basis, often in exchange for some benefit.
- Suspects: Can be a primary source of information through admissions and confessions.
Records and Documents (Written Sources):
- Public Records: Census data, vehicle registrations, property records, court records.
- Private Records: Bank statements, phone records, credit card receipts, employment records. (Often require a subpoena or search warrant to obtain).
- Police Records: Mugshot databases, modus operandi (MO) files, criminal history records.
Physical Evidence (The Crime Scene):
- The crime scene itself is a rich source of information. Physical evidence can provide clues about what happened, how it happened, and who was involved.

Board Exam Tip: Information is the starting point of every investigation. The other two "I's" are simply methods for obtaining and processing information.

Key Differences Summarized

Feature	Interview	Interrogation
Purpose	Gather Information	Obtain Confession
Subject	Victim / Witness	Suspect
Tone	Conversational	Accusatory
Environment	Anywhere	Controlled, Private

How the Three Tools Work Together: An Example

Imagine a homicide investigation:

Information: The first responding officers arrive at the scene. They get initial information from a neighbor (a witness) who says he heard a gunshot and saw a red car speeding away. This is the starting point.
Interview & Interrogation:
- Detectives interview the neighbor to get a more detailed description of the car and the timeline.
- Using motor vehicle records (Information), they find a person of interest who owns a similar red car and has a history of violence.
- They bring this person in for an interrogation. The suspect denies everything.
Instrumentation:
- The crime scene team has collected a spent cartridge case from the scene. The firearms unit (Instrumentation) identifies it as a 9mm round.
- Detectives get a search warrant for the suspect's house and car (Information). They find a 9mm handgun.
- The firearms unit test-fires the gun and, using a comparison microscope (Instrumentation), matches it to the cartridge case from the scene. This provides a scientific link between the suspect's gun and the crime.
Integration: Detectives go back to interrogate the suspect again. This time, they confront him with the ballistics match. Faced with the undeniable scientific evidence, the suspect confesses.

This example shows how the "3 I's" are not used in isolation. They are interwoven, with each tool supporting and strengthening the others, leading to the successful resolution of the case.

Introduction

A criminal investigator is like a craftsman. And like any craftsman, they have a set of essential tools they must master to be effective. In the field of criminal investigation, these primary tools are known as the "Three I's": Information, Interview & Interrogation, and Instrumentation. A successful investigation almost always involves the skillful use of all three. This module will break down each of these tools, explaining their function and importance in the quest to solve a crime.

Key Learning Objectives:

Identify and define the "Three I's" of criminal investigation.
Describe the various sources of information available to an investigator.
Differentiate between an interview and an interrogation.
Understand the role of instrumentation and its relationship to the other two tools.
Explain how the three tools work together to solve a crime.

II. Interview and Interrogation: The Human Element

Definition: This tool involves the systematic and skillful questioning of individuals to obtain information. It is the primary method for gathering information from people.

A. Interview

Definition: An interview is the simple, non-accusatory questioning of a person who is believed to have information of official interest.
Purpose: To gather facts and background information.
Subject: Typically a victim or a witness.
Tone: Conversational, friendly, and designed to build rapport and encourage cooperation. The goal is to get the person to share everything they know.
Environment: Can be conducted anywhere—at the crime scene, in a patrol car, at the person's home, or at the police station.

B. Interrogation

Definition: An interrogation is the formal and systematic questioning of a person who is a suspect or who is reluctant to cooperate.
Purpose: To obtain a confession or an admission of guilt. It is also used to gain further information about the crime or to learn the identity of accomplices.
Subject: A suspect or a hostile witness.
Tone: Accusatory and confrontational. The investigator is trying to break down the subject's resistance to telling the truth.
Environment: Always conducted in a controlled, private environment (an "interrogation room") where the investigator can control the psychological atmosphere and minimize distractions.

Key Differences Summarized | Feature | Interview | Interrogation |

III. Instrumentation: The Application of Science

Definition: Instrumentation refers to the use of the instruments and methods of the natural and physical sciences to detect and analyze physical evidence. In short, this is forensic science or the work of the crime laboratory.

A. The Role of Instrumentation

While information and interrogation deal with testimonial evidence (what people say), instrumentation deals with physical evidence (tangible objects). Its role is to provide objective, scientific facts that can:

Link a suspect to a crime scene or victim. (e.g., DNA, fingerprints, fibers).
Identify a substance. (e.g., confirming a white powder is cocaine).
Reconstruct the crime. (e.g., ballistics analysis of bullet trajectories).
Corroborate or refute testimonial evidence. (e.g., a suspect says he was never at the scene, but his fingerprints are found there).

B. Examples of Instrumentation

Dactyloscopy: Fingerprint analysis.
Forensic Ballistics: Firearms identification.
DNA Analysis: Genetic profiling.
Questioned Documents Examination: Handwriting and forgery analysis.
Forensic Chemistry: Analysis of drugs, explosives, and unknown substances.
Polygraphy: The use of the "lie detector" as an investigative aid.

Relationship to the Other Tools: Instrumentation is often the key to verifying or disproving the information gathered through interviews and interrogations. A confession (from interrogation) is powerful, but a confession combined with the suspect's DNA on the murder weapon (from instrumentation) is nearly unbeatable in court.

Conclusion

The "Three I's" are the foundational pillars of criminal investigation. Information is the raw material, Interview and Interrogation are the means of gathering it from people, and Instrumentation is the means of analyzing it from physical objects. A successful investigator must be a master of all three, knowing how to find information, how to talk to people, and how to use the power of science to uncover the objective truth.