In the annals of criminal justice, few debates are as fraught as the line between mental illness and moral culpability. The phrase “trying to play the insanity role—she’s not insane, she’s pure evil” captures a sentiment that resonates with many who have followed high-profile criminal cases. It represents a visceral public reaction that often clashes with the nuanced, clinical assessments demanded by the legal system. This tension lies at the heart of some of the most controversial trials in recent history, where defendants attempt to use an insanity defense while prosecutors, the public, and sometimes even mental health experts argue that the actions on display were not the product of a broken mind, but of an evil heart.
The Anatomy of an Insanity Defense
To understand why the claim of insanity is so often met with public skepticism, it’s important to recognize what the defense actually entails. In many jurisdictions, a defendant pleading not guilty by reason of insanity must prove that, at the time of the crime, they were unable to understand the nature and quality of their actions or that they could not distinguish right from wrong . It is a legal argument, not a medical diagnosis, and the burden of proof is often on the defense to demonstrate that a severe mental disease or defect was the direct cause of the criminal act .
This high bar is why such defenses are rarely successful. It requires clinical evidence showing that the defendant’s psychosis or delusion was so profound that it robbed them of all agency and awareness. As one forensic psychologist noted in a case where a mother killed her three children, while the defense argued for postpartum psychosis, the prosecution aimed to show that she “acted intentionally, rationally and swiftly” . The distinction often comes down to evidence of calculation and awareness versus evidence of a complete break from reality.
Cases That Defined the Debate: The “Calculated” Criminal
The recent trial of Lindsay Clancy, who was charged with killing her three children in 2023, has become a flashpoint in this debate . Her defense team openly admitted that she caused the deaths but argued that severe postpartum psychosis made her not criminally responsible . In contrast, prosecutors painted a picture of a woman who knew exactly what she was doing, citing cellphone search history for terms like “psychosis,” “sociopath,” and methods of suicide, as evidence of a mind that was contemplating its actions . For many observers, the fact that her ex-husband, who asked the public to forgive her, acknowledged she was someone who “got sick” stands in stark contrast to the prosecutor’s narrative of a calculated act. The public perception often hinges on this narrative—a grieving husband’s forgiveness is difficult to reconcile with the image of a “monster,” yet the prosecution’s evidence seems to preclude the “helpless victim of mental illness” defense.
This pattern is not unique. In the case of Mississippi teen Carly Gregg, accused of murdering her mother and attempting to kill her stepfather, a psychiatrist testified that a specific act disqualified her from an insanity defense . The act in question? After allegedly shooting her mother, Gregg used her mother’s phone to text her stepfather, “When will you be home honey?”—a deliberate trap . A psychiatrist described this as “diabolical” and argued that such a calculated, manipulative act is “not consistent with a dissociative spell, it is not consistent with psychosis” . The very action that might have been necessary to keep up a facade was the one that, in the eyes of an expert, revealed her criminal agency. This highlights a key battleground: the presence of deliberate, manipulative behavior, even in the midst of a crisis, is often seen as the antithesis of insanity.
Likewise, the case of Sheila LaBarre, a woman who killed two boyfriends, saw her defense argue she was a delusional “angel sent from God to punish pedophiles” . The prosecution, however, successfully portrayed her as a “crude, manipulative, cruel and vindictive” woman . The jury agreed, and she was found guilty and sentenced to life in prison . In each of these cases, the prosecution’s success hinged on showing that even if the defendant had mental health issues, they were not so incapacitated as to negate their responsibility. The presence of manipulation—tricking a victim, setting a trap, or lying to cover tracks—is powerful evidence that suggests a mind that is not simply “crazy,” but is actively scheming.
When the System Fails to Deliver
The anguish of victims’ families often intensifies when the insanity defense is invoked. In the case of Celeste Manno, who was stalked and murdered by a former colleague in Australia, her family was outraged when the perpetrator was sentenced to a term that, in their view, was far too lenient . The family’s raw pain was captured in a victim impact statement read in court: “He not only murdered my sweetie, but he did it under my watch. He destroyed my self worth” . The case became a powerful symbol of how the justice system can fail to protect victims and can be seen as more “merciful” to perpetrators than they ever were to their victims.
This frustration is what fuels the public narrative of “pure evil.” When a perpetrator shows no remorse, engages in elaborate premeditation, and terrorizes their victims, the suggestion that they were simply “sick” feels like an insult to the victims and an abdication of justice. As a prosecutor in one case argued, “He was brutal, he was violent, he was not insane” . The line between a mental defect and a character defect, however blurred it may be in psychology, becomes a sharp moral divide in the public eye.
Ultimately, the “insanity role” is a risky and often unpopular strategy. The public is often quick to see through what it perceives as a ploy, and when a defendant is caught in a lie or a contradictory act, the “pure evil” label becomes a near-certainty in the court of public opinion, even if it is never uttered in a legal one. The tension between the clinical and the moral will continue to define these cases, as the justice system grapples with how to hold someone accountable for actions that seem to defy comprehension.









