Critics of the Red Technique of Investigative Interviewing often suggest that evaluating a subject's credibility based on their verbal and nonverbal behaviors is an unreliable process. They base this conclusion on a series of academic studies that suggest that an investigator's assessment of a subject's truthfulness based on their verbal and nonverbal responses is no more accurate than flipping a coin - no better than chance: 50/50. In one of our Investigator Tips, The Issue of Misclassification, we detail the deficiencies with many of the academic research studies.

It should be noted that the majority of investigative decisions as to the subject's involvement in committing the act that is under investigation are based on the factual evidence developed in the case: see The Reid Behavior Analysis Interview: Part 1: Do the Case Facts and Evidence Support the Subject's Story? Part 2: The Interview Structure and the Value of Behavior Symptom Analysis.

Furthermore, it is interesting to note that attorneys and judges are trained on how to assess a witness's credibility. Consider the following: Standard legal frameworks, such as the Ninth Circuit Criminal Jury Instructions and guidelines from the Legal Information Institute, direct observation toward several core areas:

1. Demeanor and Delivery (Non-Verbal Behaviors)

Courts and practitioners observe how a witness presents themselves on the stand, though legal training increasingly emphasizes that nervous or fidgety behavior does not automatically equate to lying: [1, 2]

• Eye Contact and Focus: Whether a witness maintains an appropriate gaze or darts their eyes, avoids looking at counsel or the bench, or stares rigidly.
• Body Language and Gestures: Posture (slouching versus sitting upright), fidgeting, hand/body gestures, rocking, or pacing.
• Vocal Delivery and Tone: Hesitation, evasiveness, spontaneity, tone of voice, changes in pitch, throat clearing, or pacing of speech.
• Attitude: Confidence without arrogance, calm demeanor, or conversely, defensiveness, hostility, and over-eagerness.

2. Internal and External Consistency

Attorneys actively cross-examine witnesses to test whether their story holds together:

• Internal Consistency: Whether the witness's statements remain steady from initial depositions to direct examination and cross-examination. [1, 2]
• External Consistency (Corroboration): Whether the testimony lines up with objective, independent evidence, such as documents, physical exhibits, digital records, or other reliable testimony. [1, 2, 3]
• Explanations for Inconsistencies: How a witness accounts for gaps or contradictions if they arise. [1]

3. Opportunity and Ability to Perceive

Judges evaluate the physical and mental foundation of the testimony:

• Sensory Opportunity: Whether the witness actually had the chance, lighting, distance, and unobstructed view to see or hear what they claim.
• Memory and Clarity: The strength, sharpness, and clarity of the witness's recall regarding details.
• Capacity: The witness's mental competence to perceive, remember, and accurately narrate the events. [1, 2, 3, 4]

4. Bias, Motive, and Interest

Attorneys and judges look for hidden or overt influences that might slant a testimony:

• Financial or Personal Stake: Whether the witness has a direct interest in the outcome of the case (e.g., financial gain, liability, or self-preservation).
• Relationships: Existing biases, loyalties, or animosity toward the parties involved.
• "Hired Gun" Status: In expert testimony, whether the expert appears objective or overly aligned with the paying side.

5. Reasonableness and Plausibility

• Plausibility: Whether the narrative makes logical, common-sense sense in light of human behavior and the surrounding facts of the case.

Also see the National Institute of Justice.