There are times when an act of crime is a result of a psychiatric disorder, but suffering from one does not mean that a person can act unlawfully without being held accountable.
In certain circumstances or jurisdictions, mental disorders may play a role in the determination of an insanity defense, whether an individual is fit to stand trial, or whether the prosecution has indeed proven the mens rea element of the offense.
Within the federal court system, a specific statutory provision governs the issue of insanity. Meanwhile, the issue of competency mainly concerns the defendant’s mental competence to understand the trial process and to assist in their defense.
The latest national data show that millions of American adults experience mental illness each year, although the prevalence of mental illness should not be confused with the much narrower legal standards required for an insanity or competency determination.
Let’s find out how a mental illness defense differs from competency and what a defendant must prove to use a mental health-related defense.
Competency Is a Different Question Than Guilt
Before a case can even proceed, a court has to be satisfied that the defendant understands what’s going on in the proceedings against them and that they can actually help with their defense. This is competency to stand trial, which is unrelated to what happened at the time of the alleged offense.
A person who was in control of their senses during the commission of a crime may still be found unfit to stand trial some period after some intervening condition occurs. Some instances of eligible medical conditions comprise actual mental disturbances, moderate or severe cognitive impairments, or a traumatic brain injury. These conditions may prevent an individual from understanding what is happening or interacting productively with their lawyer.
Someone who was fully aware of what they were doing when the crime occurred can still be found incompetent to stand trial months later if some condition interferes. Examples of qualifying conditions include acute psychosis, a serious cognitive impairment, or a traumatic brain injury. In that moment, they might not understand the proceedings or communicate meaningfully with their attorney.
When competency becomes a question, courts usually order a psychological evaluation. If the court finds incompetence, it doesn’t just end the matter or clear the underlying charge. Instead, it pauses the case. Depending on the jurisdiction, it can set up treatment meant to restore competency first before the case moves forward again.
The Insanity Defense Is Narrow and Rarely Used
Most people have heard of the insanity defense since it is probably the most famous example of mental illness and criminal responsibility intersecting, but oftentimes, this defense is misunderstood. According to 18 U.S.C. § 17, the defendant must prove by clear and convincing evidence that, as a result of a severe mental disease or defect, he or she was unable to appreciate the nature and quality of the wrongfulness of the criminal conduct at the time of the offense.
That test replaced an earlier, broader one too. The older idea could excuse conduct someone couldn’t really control even if they knew it was wrong, so it really left only the tighter question of whether the person understood what they were doing in the first place.
Even with all the attention it gets in pop culture, the insanity defense is brought up in well under one percent of criminal cases across the country. Research keeps showing that it works only about a quarter of the time once it’s actually invoked. A mental illness diagnosis alone is never enough.
The defense requires expert testimony establishing both the severity of the condition and its direct connection to the defendant’s ability to understand their conduct at the precise time of the offense.
Mental Illness Can Matter Even Without Meeting That Standard
A condition that lands below the insanity defense’s strict threshold can still end up shaping a case in real ways. For example, evidence of a mental health condition can help support an argument that a defendant didn’t have the specific intent a charge requires. It can also play into how a prosecutor looks at the case, especially during plea negotiations. It may even sway a judge’s sentencing decision after a conviction.
Attorneys who deal with these matters often team up with psychologists, psychiatrists, and other forensic professionals to show how a documented condition affected the defendant’s judgment, their perception, or their capacity to restrain their actions in the particular circumstances surrounding the offense.
How This Plays Out in a Specific Statute
Michigan’s domestic violence statute offers a concrete illustration of how these doctrines interact with a real charge. Under M.C.L. Section 750.81(2), a first offense carries a maximum of 93 days and a $500 fine, while a second offense increases the maximum to one year and a $1,000 fine, and a third offense becomes a felony.
A domestic violence 2nd offense in Michigan, which is tied to the underlying assault or battery charge it builds on, requires the prosecution to prove that the defendant intended to commit the act. One’s legal culpability is dependent on whether they had the requisite state of mind when the act constituting the offense was committed. One can be found to be criminally insane or mentally handicapped if it is proven that they cannot grasp the full extent of the wrongful act committed, making an insanity defense for the defendant possible.
It is a narrow and highly evidence-based argument that ends up requiring expert witness testimony in its support.
Why This Requires Careful, Individualized Legal Guidance
Since a mental health condition can matter at several different stages of a case and the legal standards governing each stage are distinct and often demanding, evaluating whether and how to raise mental illness in a criminal case is not something that follows a simple formula.
A mental illness defense has to be built around the specific facts of the case. One should understand to what extent the environment and the evidence shape the context. In some cases, it may be important to know whether the person accused once acted in this way. An experienced counsel is an added advantage in such situations. The lawyer will fight for the protection of this aspect of the defendant’s rights. He or she will see to it that the defendant’s interests are put across to the court.
