Many countries have a Mental Health Law that includes a wide variety of legal topics and pertain to people with a diagnosis or possible diagnosis of mental illness. Laws relating to mental illness may include criminal laws, including laws governing fitness for trial or execution.
It is a pertinent question whether persons with severe mental illness should stand for trial and ultimately risk a sentence of capital punishment.
People with serious mental illness are at a substantial disadvantage in defending themselves when they face criminal charges so serious that the death penalty is a possible outcome. The legal system may too often fail to do justice e.g. due to stigma or lack of knowledge about mental illness. In most countries the current system of fact-finding in capital cases fails to identify who among those facing a possible death penalty actually has a mitigating mental health condition. This failure is the result of several factors that work in concert: defense counsel and counsel’s staff often do not have sufficient time, experience with mental illness, Further persons suffering from mental illness may have lesser access to competent legal help and be faced with insufficient safeguards to protect their fundamental rights. As a result, people with mental illness may run a higher risk for losing their lives to unfair application of the death penalty. In the US, it is estimated that at least 20 percent of people on death row have a serious mental illness
Mental health conditions should be taken into account during all phases of a death penalty case and sufficient diagnostic evaluations be carried out to identify possible serious mental illness.
It has been argued (e.g. the US Supreme Court) that a defendant’s mental illness must be taken into consideration as an important reason to spare his or her life. However, as was initially the case with intellectual disability and young age, the Court has not barred the death penalty for those with serious mental illness and there is no constitutional prohibition against executing a person suffering from mental illness. Prohibiting the death penalty for the intellectually disabled and for juveniles due to that these groups belong to identifiable groups with diminished responsibility for their actions. But most people with mental illness — including many with severe mental illness — are not mentally incompetent.
On the other hand, many mental health experts believe that people with severe mental illness such as schizophrenia and bipolar disorder may have similar cognitive impairments that interfere with their decision-making. Regardless of whether a defendant is able to show the causation required by the insanity defense, he or she should not be threatened or put to death while suffering serious mental illness. https://www.mhanational.org/issues/position-statement-
Banning death penalty for offenders suffering from severe mental illness at the time of the offense is still debated in legal systems despite the fact that several professional organisations such as psychiatric or bar associations advocate for aa ban. The American Psychiatric Association and the American Bar Association, among others, have called for a ban on the death penalty for those with severe mental illness.