When Character Becomes Evidence: Understanding Stoll Evaluations in California Criminal Cases

“The law seeks facts, but understanding human behavior often requires context.” This principle reflects an enduring tension within the criminal justice system. Courts are tasked with evaluating conduct, yet human behavior rarely exists in a vacuum. Jurors often want to know not only what happened, but who the accused person is. The challenge, of course, is determining how much information about an individual’s character should be permitted in a courtroom without unfairly prejudicing the proceedings.

California courts have grappled with this question for decades. One of the most significant decisions addressing this issue emerged from the California Supreme Court's ruling in People v. Stoll (1989), a case that continues to shape the way psychological evidence is introduced in criminal proceedings involving allegations of sexual misconduct. More than three decades later, Stoll evaluations remain a powerful but often misunderstood tool available to criminal defense attorneys.

Understanding the legal foundation behind these evaluations is critical for attorneys who are navigating cases where personality characteristics, behavioral tendencies, and psychological functioning may provide important context to the allegations before the court.

What Is a Stoll Evaluation?

A Stoll evaluation is a forensic psychological assessment designed to evaluate whether an individual demonstrates personality characteristics that are consistent or inconsistent with a deviant sexual disposition. The evaluation derives its name from People v. Stoll (1989), in which the California Supreme Court considered whether psychological testimony regarding a defendant's personality traits could be admitted in a criminal case involving allegations of child molestation.

Prior to Stoll, courts frequently approached this type of testimony with skepticism, often viewing personality evidence as a form of improper character testimony. The California Supreme Court took a different view. The Court recognized that trained mental health professionals could offer scientifically informed opinions regarding an individual's psychological characteristics, provided those opinions were relevant, reliable, and helpful to the trier of fact.

Importantly, the Court did not create a mechanism for psychologists to determine guilt or innocence. Rather, it acknowledged that psychological evidence may assist jurors in understanding whether a defendant exhibits characteristics commonly associated with the alleged conduct.

The result was the development of what practitioners now commonly refer to as a "Stoll evaluation."

The Relationship Between Stoll and California Evidence Code §1102(a)

To understand why Stoll evaluations remain relevant today, attorneys must also understand California Evidence Code §1102(a).

Section 1102 (a) permits criminal defendants to introduce evidence of their own character or traits of character when those traits are relevant to the charged offense. Once the defense introduces such evidence, the prosecution may offer evidence to rebut it under §1102(b) .

This provision creates an important strategic opportunity. In certain cases, a defense attorney may seek to present evidence suggesting that a client possesses personality characteristics that are inconsistent with the alleged behavior. Psychological testing, structured interviews, and collateral information can provide a more objective framework for evaluating those traits than testimony from friends, family members, or community members alone.

Stoll evaluations often serve as a mechanism through which this character evidence can be presented. Rather than relying exclusively on subjective impressions, attorneys may introduce findings derived from standardized psychological assessment instruments and forensic evaluation methods.

This distinction matters. Jurors frequently expect expert testimony to be grounded in methodology rather than personal opinion. A properly conducted Stoll evaluation provides a structured and empirically informed approach to addressing questions that might otherwise be left entirely to speculation.

What Does a Stoll Evaluation Typically Examine?

Although methodologies vary depending on the referral question and evaluator, most Stoll evaluations involve several core components.

The evaluation typically includes a detailed clinical interview examining developmental history, family background, relationship functioning, sexual history, mental health symptoms, and behavioral patterns. The evaluator may also review collateral records, including police reports, witness statements, educational records, treatment records, and employment history.

Psychological testing often forms an important component of the assessment. Instruments such as the MMPI-3 (Minnesota Multiphasic Personality Inventory-3) and MCMI-IV (Millon Clinical Multiaxial Inventory-IV) may be utilized to evaluate personality functioning, emotional adjustment, behavioral tendencies, and potential psychopathology. The evaluator then integrates these findings with interview data and collateral information to formulate opinions regarding relevant personality characteristics.

Contrary to common misconceptions, a Stoll evaluation is not a lie detector, nor is it a test that determines whether someone committed an offense. The purpose is considerably narrower. The evaluation focuses on psychological characteristics and whether those characteristics are consistent or inconsistent with patterns commonly associated with the alleged conduct. To put it simply, a Stoll evaluation compares an individual's unique personality profile against psychological benchmarks to see if they possess the deep-seated emotional or behavioral traits typically seen in these types of cases.

How Defense Attorneys Can Use Stoll Evaluations

For defense counsel, the utility of a Stoll evaluation extends beyond simply generating a report.

First, the evaluation may provide an independent psychological perspective regarding the defendant's personality structure and functioning. In cases where allegations hinge heavily on credibility assessments, understanding the defendant's psychological presentation can help attorneys evaluate potential strengths and vulnerabilities within the case.

Second, a favorable Stoll evaluation may support a defense theory that the defendant lacks psychological characteristics commonly associated with the alleged conduct. Although the evaluation does not determine guilt or innocence, it may provide jurors with additional information regarding the defendant's personality functioning and behavioral tendencies.

Third, the evaluation can assist attorneys in preparing for cross-examination of opposing experts. A comprehensive Stoll assessment often identifies alternative explanations for behavior, highlights methodological concerns, and clarifies the limits of psychological conclusions that may be presented by the prosecution.

Finally, Stoll evaluations can serve an educational function. Jurors often enter the courtroom with assumptions regarding how individuals accused of sexual misconduct "should" look, act, or think. Psychological evidence may help challenge simplistic stereotypes by providing a more nuanced understanding of personality functioning.

Important Limitations Attorneys Should Understand

Like any forensic tool, Stoll evaluations have limits.

A Stoll evaluation cannot determine whether an alleged offense occurred. It cannot identify truthfulness with certainty. It cannot establish innocence. Nor can it substitute for factual evidence presented during trial.

Attorneys should be cautious of experts who overstate what psychological testing can conclude. The strongest forensic opinions are often those that clearly acknowledge the boundaries of the data. Stoll evaluations should address personality characteristics and psychological functioning. It should not become a vehicle for broad speculation regarding ultimate legal issues reserved for the jury. Courts generally find expert testimony most persuasive when it remains disciplined, transparent, and grounded in the actual scope of the evaluation.

What Prosecutors Should Keep in Mind

From the prosecution's perspective, Stoll evaluations warrant careful review rather than automatic dismissal.

The existence of a favorable Stoll evaluation does not necessarily mean the underlying allegations lack merit. Psychological characteristics alone cannot prove or disprove criminal conduct. Human behavior is complex, and individuals do not always act in ways that align neatly with personality profiles.

At the same time, prosecutors should recognize that Stoll evaluations may raise legitimate questions regarding assumptions embedded within a case. If psychological evidence is being offered, the focus should remain on methodology, data sources, testing procedures, and the reasoning process used by the evaluator.

The most effective response is not to attack the concept of forensic personality assessment itself, but to carefully examine whether the particular evaluation was conducted in a scientifically sound and legally appropriate manner.

Ultimately, both sides benefit when psychological evidence is subjected to rigorous scrutiny. The goal is not advocacy disguised as science, but science presented in a manner that assists the trier of fact.

Conclusion

More than thirty-five years after People v. Stoll, the decision continues to influence how California courts approach psychological evidence relating to character and personality functioning. For defense attorneys, a properly conducted Stoll evaluation may provide valuable context regarding a client's psychological characteristics and may assist in presenting evidence permitted under California Evidence Code §1102(a). For prosecutors, these evaluations highlight the importance of carefully evaluating both methodology and scope.

Like all forensic assessments, Stoll evaluations are most useful when they remain grounded in empirical evidence, transparent methodology, and clearly defined legal questions. When used appropriately, they can help courts move beyond assumptions and toward a more informed understanding of the individual standing before them.