In January, Dylann Roof was sentenced to death for killing nine black churchgoers at a prayer meeting in Charleston, S.C. Since then, some commentators have debated whether Roof should have had the right to fire his attorneys when they wished to introduce evidence of mental illness — and whether, or when, mental illness should disqualifysomeone for capital punishment.

Most Americans oppose the death penalty for the mentally ill, a category that ranges from mild to severe. But our research suggests that the death penalty actually targets those who have mental illnesses.

People who are executed have a far higher rate of mental illness than does the general public.

Suicidal tendencies are particularly common. For instance, evidence suggests that Roof had intended to shoot himself at the Emanuel African Methodist Episcopal Church after the killings. When that failed, he refused legal defense in the penalty phase of his trial. If a judge allows, he may refuse any legal appeals, thus committing suicide by execution.

[U.S. executions and death sentences dropped dramatically in 2016 — except in a few hotspots]

Roof would be far from the first to do so. Since 1976, the United States has executed 1,448 inmates; 141 of these have been “volunteers,” those who waive appeal. If suicidal tendencies are evidence of mental illness, then death penalty states actively assist suicide.

Several states are considering banning the execution of people with severe mental illnesses or brain injuries. In March 2016, the state of Texas executed Adam Kelly Ward, whose bipolar disorder had been diagnosed when he was 4, for shooting a city inspector, whom he apparently believed was threatening his family.

As Shaila Dewan of the New York Times reported, “The U.S. Supreme Court has previously barred the execution of inmates who are so mentally impaired that they do not comprehend that they are going to be executed, but it has stopped short of outright banning the execution of the mentally ill.”

[For more of this story, written by Frank R. Baumgartner and Betsy Neill, go to https://www.washingtonpost.com...m_term=.c5d099b55ac0]