The Role of Forensic Psychologists in Criminal Defense Cases

July 24, 2025
By Lessem, Newstat & Tooson, LLP

At Lessem, Newstat & Tooson, LLP, we understand that criminal defense cases require a multifaceted approach to ensure the best possible outcome for our clients. One critical component of a robust defense strategy is the involvement of forensic psychologists. These specialized professionals bridge the gap between psychology and the legal system, providing invaluable insights that can shape the trajectory of a case.

What Is a Forensic Psychologist?

Forensic psychologists are trained mental health professionals who apply their expertise in human behavior to legal matters. Unlike clinical psychologists who focus on therapy and mental health treatment, forensic psychologists work within the judicial system, offering objective assessments and expert opinions. They hold advanced degrees in psychology, often with specialized training in forensic applications, and are skilled in evaluating individuals involved in legal proceedings.

In criminal defense cases, forensic psychologists provide critical services, including psychological evaluations, expert testimony, and consultation with defense attorneys. Their work helps uncover mental health factors that may influence a defendant’s actions, competency, or culpability, ultimately aiding in the pursuit of justice.

Key Responsibilities of Forensic Psychologists in Criminal Defense

Forensic psychologists contribute to criminal defense cases in several impactful ways. Their expertise ensures that mental health considerations are thoroughly explored and effectively presented in court. 

Below are some of their primary responsibilities:

1. Assessing Competency to Stand Trial

One of the most critical roles of a forensic psychologist is evaluating a defendant’s competency to stand trial. Competency assessments determine whether a defendant has the mental capacity to understand the charges against them and participate meaningfully in their defense. This involves assessing the defendant’s ability to comprehend legal proceedings, communicate with their attorney, and make informed decisions.

Forensic psychologists use standardized tools and clinical interviews to evaluate cognitive and psychological functioning. If a defendant is found incompetent due to mental illness or intellectual disability, the court may delay the trial or order treatment to restore competency. This ensures that the legal process upholds fairness and protects the defendant’s rights.

2. Evaluating Criminal Responsibility (Insanity Defense)

In some cases, forensic psychologists assess whether a defendant was legally insane at the time of the alleged offense. The insanity defense hinges on proving that the defendant could not distinguish right from wrong or control their actions due to a severe mental disorder. Forensic psychologists conduct detailed evaluations, reviewing medical history, psychological testing, and behavioral evidence to form an expert opinion.

While the insanity defense is rare and often misunderstood, a forensic psychologist’s thorough assessment can provide clarity and support a defense strategy that emphasizes diminished responsibility. Their findings can influence plea negotiations, sentencing, or the overall direction of the case.

3. Conducting Risk Assessments

Forensic psychologists often perform risk assessments to evaluate the likelihood of a defendant reoffending or posing a danger to society. These assessments are particularly relevant during sentencing or parole hearings. By analyzing factors such as past behavior, mental health conditions, and environmental influences, forensic psychologists provide data-driven insights that help courts make informed decisions about incarceration, probation, or rehabilitation programs.

For defense teams, risk assessments can support arguments for leniency, such as advocating for mental health treatment or alternative sentencing options instead of prolonged imprisonment.

4. Providing Expert Testimony

Forensic psychologists frequently serve as expert witnesses, presenting their findings to judges and juries in a clear and authoritative manner. Their testimony can explain complex psychological concepts, such as the impact of trauma, mental illness, or cognitive impairments, in a way that is accessible to non-experts. This helps the court understand the defendant’s mental state and its relevance to the case.

At Lessem, Newstat & Tooson, LLP, we collaborate closely with forensic psychologists to reinforce our arguments and enhance the credibility of our case.

5. Mitigation in Sentencing

In cases where a conviction is likely, forensic psychologists play a vital role in the sentencing phase by providing mitigation evidence. They may identify factors such as childhood trauma, substance abuse, or untreated mental health conditions that contributed to the defendant’s behavior. By presenting a comprehensive psychological profile, they help humanize the defendant and advocate for a fair and proportionate sentence, such as treatment programs or reduced penalties.

6. Supporting Mental Health Diversion

Forensic psychologists also prepare reports and evaluations to support mental health diversion programs, which allow eligible defendants with mental health disorders to receive treatment instead of incarceration. These reports assess the defendant’s mental health condition, treatment needs, and suitability for diversion programs. By providing detailed psychological insights, forensic psychologists help demonstrate that diversion is a viable alternative, potentially leading to case dismissal upon successful completion of treatment. This approach not only benefits the defendant by addressing underlying mental health issues but also promotes public safety through rehabilitation.

7. Consulting with Defense Attorneys

Beyond evaluations and testimony, forensic psychologists consult with defense attorneys to develop case strategies. They offer insights into the defendant’s mental health, suggest potential defenses, and identify areas where psychological evidence could strengthen the case. Their expertise helps attorneys craft compelling defenses that resonate with judges and juries.

Why Forensic Psychologists Are Essential to Criminal Defense

The inclusion of a forensic psychologist in a criminal defense case can be a game-changer. Their objective assessments provide a scientific basis for arguments that might otherwise be overlooked.

By addressing mental health issues, they ensure that the court considers the full context of a defendant’s actions, which can lead to:

  • Dismissal or Reduction of Charges: Demonstrating mental health issues or incompetence may result in charges being dropped or reduced.
  • Fair Sentencing: Mitigation evidence can lead to lighter sentences or alternative penalties focused on rehabilitation.
  • Protection of Rights: Competency evaluations safeguard defendants from being tried unfairly due to mental incapacity.
  • Diversion Opportunities: Mental health diversion programs, supported by forensic evaluations, can lead to treatment-focused resolutions, avoiding traditional prosecution.

At Lessem, Newstat & Tooson, LLP, we recognize that every case is unique and ensure that our clients receive comprehensive representation that accounts for all relevant factors, including mental health.

Challenges and Considerations

While forensic psychologists provide invaluable expertise, their involvement comes with challenges. Their findings must be objective and withstand scrutiny from opposing counsel. Additionally, psychological evaluations can be complex, requiring careful coordination between the psychologist, defense team, and client. At our firm, we work diligently to select highly qualified forensic psychologists and integrate their work seamlessly into our defense approach.

It’s also worth noting that the use of psychological evidence must be strategic. Overreliance on mental health arguments without sufficient evidence can weaken a case, while underutilizing this resource may miss opportunities to strengthen the defense. Our experienced attorneys carefully balance these considerations to maximize the impact of forensic psychology in court.

How Lessem, Newstat & Tooson, LLP Leverages Forensic Psychology

At Lessem, Newstat & Tooson, LLP, we are committed to providing top-tier legal representation for our clients facing criminal charges. Our team collaborates with mental health experts to build strong, evidence-based defenses. Whether it’s securing a competency evaluation, presenting mitigation evidence, supporting mental health diversion, or challenging the prosecution’s narrative, we leverage the expertise of forensic psychologists to advocate for the best possible outcomes.

Our approach is client-centered and thorough. We take the time to understand the unique circumstances of each case, ensuring that psychological evaluations are tailored to our clients’ needs. By combining legal acumen with psychological insights, we create compelling defense strategies that uphold our clients’ rights and dignity.

If you or a loved one is facing criminal charges, contact Lessem, Newstat & Tooson, LLP today. Let our experienced team fight for your rights and work toward a favorable resolution.

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