I took the data in the paper "Killing the Willing: "Volunteers," Suicide and Competency" and drew this chart.
The paper is fascinating. It observes that although blacks are disproportionately represented in executions versus the general population, volunteers to be execute-- i.e. people who waived their appeals-- are overwhelmingly white, male, and have psychiatric illnesses, especially borderline, depression, and psychoses (and an additional 10% have substance abuse)-- which is basically your demographic for suicide attempts. 30% also had prior suicide attempts.
So the author asks: if there is no such right to assisted suicide (indeed, any suicide at all), can there ever be a waiver of the appeal in capital cases? Even if the defendant is competent, if suicide is a motivation, the author writes, "their decisions should not, indeed must not, be honored, at least so long
assisted suicide is not available to other persons in the jurisdiction."
The counter argument, of course, is that competency is a legal matter, and the person's motivations beyond that are irrelevant. For example, if a guy is sentenced to prison and wants to go, he still goes.
McClesky v. Kemp (1987) attempted to abolish the death penalty under the argument that executions were influenced by racial discrimination. This was rejected. But Atkins v. Virginia (2002) did abolish the executions of the mentally retarded. Consequently, abolition of the death penalty, or at least a drastic curtailing of it, is more likely to occur along lines of competency and mental state, rather than any appeal to morality, race, or class.
I thought I knew how I felt about this issue, and now I am not so sure. But before anyone forms their opinion, I would strongly urge everyone to read the dissent by Scalia in the Atkins case. It should be required reading for every psychiatrist, whether you agree with him or not.