Disorders & Testimony Reliability

Why Language, Cognition, and Speech Skills Can Make or Break a Legal Case

Introduction

In legal proceedings, testimony reliability is often treated as a matter of credibility, honesty, or psychological functioning. However, one critical factor is frequently overlooked:

Communication disorders. Speech, language, and cognitive-communication impairments can significantly affect how an individual understands questions, recalls events, organizes responses, and expresses information—without any intent to deceive.

As a forensic speech-language pathologist, I evaluate how communication disorders directly impact testimony reliability, Miranda comprehension, interview performance, and courtroom communication.

This article explains why communication matters, which disorders affect testimony, and how forensic speech-language pathology fills a major gap in legal evaluations.

What Is Testimony Reliability?

Testimony reliability refers to whether a statement is:

• Accurately understood

• Internally consistent

• Chronologically organized

• Free from undue suggestibility or coercion

• Communicated clearly and coherently

Importantly, reliability ≠ truthfulness.

The truth is, a person can be honest yet unreliable due to language processing, memory, executive functioning, or speech impairments.

Communication Disorders That Affect Testimony Reliability

Cognitive-Communication Disorders

Often caused by:

• Traumatic brain injury (TBI)

• Stroke

• Neurodegenerative disease

• Hypoxia

• Long COVID

• Tumors or neurological illness

These impair:

• Attention and working memory

• Processing speed

• Narrative organization

• Cause-and-effect reasoning

Legal impact:✔ Inconsistent timelines✔ Slowed responses interpreted as evasion✔ Difficulty following complex or compound questions

Language Disorders (Aphasia & Language Impairment)

Language disorders affect the ability to understand and/or express language, not intelligence.

Signs include:

• Word-finding difficulty

• Misinterpretation of questions

• Limited vocabulary

• Fragmented or vague responses

Legal impact:✔ Misunderstanding Miranda rights✔ Incorrect yes/no responses✔ Apparent contradictions that reflect language breakdown, not deception

Executive Function & Pragmatic Language Deficits

Executive functioning governs:

• Planning

• Inhibition

• Self-monitoring

• Social communication (pragmatics)

Common in:

• Autism

• ADHD

• TBI

• Psychiatric and neurodevelopmental conditions

Legal impact:

✔ Over-disclosure or under-disclosure

✔ Difficulty adjusting answers

✔ Poor conversational repair

✔ Increased vulnerability to coercive questioning

🔁 Suggestibility & Vulnerability

Some individuals are highly suggestible due to:

• Cognitive limitations

• Language processing deficits

• Trauma history

• Developmental disorders

Legal impact:

✔ Compliance with leading questions

✔ Adoption of examiner language

✔ Increased risk of false or unreliable statements

Why Psychological Evaluations Are Not Enough

Psychological and neuropsychological evaluations are essential—but they do not directly assess functional communication in legal contexts.

They often do not evaluate:

• Real-time language comprehension

• Pragmatic communication

• Narrative discourse

• Question-answer breakdowns

• Speech intelligibility under stress

This is where forensic speech-language pathology is uniquely positioned.

What a Forensic Speech-Language Pathologist Evaluates

A forensic SLP assesses how communication abilities impact legal participation, including:

• Understanding of rights and questions

• Ability to provide accurate narratives

• Processing speed and response formulation

• Consistency vs communication breakdown

• Vulnerability to coercion

• Functional courtroom communication

These findings directly inform:

• Competency evaluations

• Suppression motions

• Credibility interpretation

• Trial strategy

• Accommodations and safeguards

Why Attorneys Need Communication-Based Analysis

When communication disorders are missed:

• Statements may be misinterpreted

• Clients may appear deceptive or evasive

• Vulnerable individuals may be unfairly penalized

• Due process may be compromised

A forensic communication analysis ensures testimony is evaluated through an ability-based lens, not assumptions.

Learn more about forensic speech-language pathology here.

About the Author

Erica Thomas, MS, CCC-SLP is a nationally licensed Speech-Language Pathologist specializing in forensic communication evaluation, adult neurogenic disorders, and high-stakes legal communication.

She provides expert evaluation and consultation for criminal defense, civil litigation, immigration, and complex medico-legal cases across the United States.

📍 Licensed in: AZ, CA, CO, FL, NM, PA, VA, WA📞 Nationwide consulting available (record review in non-licensed states)

📩 Attorney & Professional Inquiries

If your case involves:

• Inconsistent statements

• Miranda comprehension concerns

• TBI or neurological injury

• Autism or developmental disorders

• Vulnerability to coercion

A forensic communication evaluation may be critical.

Contact: www.ejtcommconsult.com