On May 24, 2016, United States Attorney General Loretta Lynch announced that the Justice Department would seek the death penalty against Dylann Roof, charged with a federal hate crime in conjunction with the murder of nine African American worshippers in a Charleston, South Carolina church. A state grand jury indicted Roof for the murders and prosecutors have announced they also will seek the death penalty. The federal prosecution would follow the state trial.

While it is unlikely that as many South Carolinians will oppose the death penalty as did Massachusetts residents on the eve of Dzhokhar Tsarnaev’s trial, the procedure for empanelling a jury will follow the same rules. Those rules tilt the scales toward death.

Dzhokhar Tsarnaev’s terrorist rage turned the finish line of the 2013 Boston Marathon into a killing field. His calculated murder of innocents horrified people throughout the United States. Yet on the eve of his trial, less than 20% of Massachusetts residents polled said Tsarnaev should be put to death and 66% of Boston residents stated they favored a life sentence. A jury that must choose between life imprisonment and capital punishment, U.S. Supreme Court Justice Potter Stewart wrote in an earlier capital case, “can do little more – and must do nothing less – than express the conscience of the community on the ultimate question of life or death.”

The discordance between the Boston jury’s decision sentencing Tsarnaev to death and the community’s conscience wasn’t a quirk. The federal government, as well as every state with the death penalty, requires a capital jury to be death-qualified, to be purged of jurors who have reservations about imposing the death penalty. Prosecutors are permitted to exclude jurors who hold conscientious scruples against imposing the death penalty, even in the absence of evidence that a juror’s scruples would interfere with his ability to determine guilt in accordance with the law. This controversial practice allows prosecutors to create a jury that critics say is prone to convict and quick to impose a death sentence rather than life imprisonment without the possibility of parole. Proponents of the death penalty respond by arguing the state has a right to a jury that will follow the law.

At the peak of its due process revolution, the Warren Court challenged the practice of death-qualifying a capital jury when it ruled in Witherspoon v. Illinois (1968) that a potential juror who held conscientious scruples against the death penalty could not be excluded for that reason alone. In the 1980s, however, Justice William H. Rehnquist, who President Richard Nixon pointed out proudly at the time of his appointment to the Court, was “a reactionary bastard,” led an assault against Witherspoon. He authored a dissent and two major decisions that drastically eroded a capital defendant’s constitutional right to an impartial jury and dramatically increased the odds a jury would opt to impose the death penalty. Rehnquist’s campaign brought the Supreme Court’s position on death-qualifying perilously close to legitimizing a hanging jury.

At the time of Witherspoon’s trial for the murder of a police officer, Illinois law armed the prosecutor with unlimited challenges in order to exclude those jurors who “might hesitate to return a verdict inflicting death.” In rapid succession forty-seven scrupled jurors were dismissed. No effort was made to determine if a juror’s conscientious scruples would automatically lead him to vote against a sentence of death. Witherspoon was convicted and sentenced to death. The U.S. Supreme Court granted review of his death sentence.

Writing for the majority, Justice Stewart, an Eisenhower appointee, condemned Witherspoon’s jury. He argued it fell well short of the impartiality a defendant was entitled to under the Sixth Amendment and that it failed to express the conscience of the community. “No defendant can constitutionally be put to death,” Stewart argued, “by a tribunal so selected.” The Court reversed Witherspoon’s death sentence.

In 1972 the Court struck down the death penalty in Furman v. Georgia, declaring that its application was unconstitutionally arbitrary. All but a handful of states responded by rewriting death penalty laws intended to limit the arbitrariness of the punishment. Four years later, the Court upheld a number of these revised statutes in Gregg v. Georgia. Under the new rules death penalty trials are divided into two phases: the guilt/innocence phase and the penalty phase. If the defendant is found guilty the jury considers evidence of mitigating circumstances presented by the defense and the prosecution presents aggravating circumstances. The jury weighs these contradictory arguments and decides whether to sentence the defendant to death.

When the Supreme Court turned its attention to the issue of death-qualified juries in Adams v. Texas (1980), a case tarred with the brush of prosecutorial misconduct, a majority of the Court held that scrupled jurors had been excluded contrary to Witherspoon, but Rehnquist dissented. At the time of Witherspoon, he wrote, states gave juries complete discretion in considering the death penalty. Since the Court’s decision in Gregg, “it’s hard to imagine a system of capital sentencing that leaves a jury less discretion.” Therefore, Rehnquist concluded, Texas is “entitled to require each juror to swear that he/she will adhere to the stated rules without regard to the possible imposition of a death sentence.”

In 1985, Johnny Paul Witt was convicted of first-degree murder in Florida and sentenced to death. However, the U.S. Court of Appeals agreed with Witt’s claim that at least one prospective juror had been improperly excluded for cause because of his opposition to the death penalty. Following the Witherspoon criteria the Appeals Court reversed Witt’s death sentence.

Writing for the majority, Rehnquist reversed the Appeals Court and made three rulings that effectively gutted the Witherspoon standard. First, he swept aside the requirement that a juror could not be struck unless he made it “unmistakably clear that he would automatically vote against the imposition of the death penalty without regard to any evidence.” In its place, he substituted a rule allowing a prosecutor to exclude a potential juror if his views “would prevent or substantially impair the performance of his duties.” Second, a juror’s bias against imposition of the death penalty did not need to be proved with “unmistakable clarity,” but was up to the trial judge to determine. Third, he ruled that a potential juror’s answers to a trial judge’s questions were “factual” and therefore, “uncontestable” by an appeals court.

One year later, Rehnquist returned to what he termed were “questions left open by Witherspoon.” In Lockhart v. McCree he acknowledged the existence of more than a dozen studies showing that removing jurors with conscientious scruples resulted in “a conviction prone jury.” But, he wrote, even if death-qualified juries were “somewhat more” conviction-prone than non-death qualified juries, “the Constitution does not prohibit the states from death-qualifying juries in capital cases.” He also ruled that death-qualifying a capital jury did not violate the Sixth Amendment requirement that a jury be drawn from a fair cross-section of the community. The fact is, he said, people with conscientious scruples against the death penalty were not a “distinctive community group.”

Justice Thurgood Marshall rejected Rehnquist’s style and his arguments. “With a glib nonchalance ill-suited to the gravity of the issue presented and the power of [McCree’s] claims,” Marshall wrote, “the Court upholds a practice that allows a State a special advantage in those prosecutions where the charges are the most serious and the possible punishment the most severe.” Without doubt, he concluded, death-qualifying a jury makes it more likely to convict and to sentence a defendant to death.

In the decades after the Warren Court made the inclusion of jurors with conscientious scruples a part of capital due process, two Rehnquist opinions eliminated the death-qualified rules laid down in Witherspoon and in the process distorted the jury’s fundamental purpose. A jury that excludes nearly half of the people in the United States because they have conscientious scruples against the death penalty cannot be said to represent a fair cross section of the community, nor fulfill the Sixth Amendment’s command to impanel an impartial jury. For those reasons alone, death-qualifying a jury violates the Supreme Court’s oft-articulated guiding principle: the death penalty is “qualitatively different” from all other punishments and, therefore, it requires extraordinary procedural protection against error and arbitrariness.