The complicated and uncertain moral calculus that is demanded of jurors in every capital case played out in Boston when the jury voted to impose death for the people he was found directly responsible for killing when he placed one of the two bombs: Martin Richard and 23-year-old Boston University graduate student Lingzi Lu. Yet the jury did not impose death as a punishment for the murder of another victim, Krystle Campbell, perhaps because her death was caused by the bomb planted by Tamarlin or for murder of MIT Police Officer Sean A. Collier, whom the defense argued was shot to death by Tamerlan, not Dzhokhar. By what moral calculus was Dzhokhar Tsarnaev any less culpable for their deaths?

The Tsarnaev verdict should remind us of how demanding such judgments are and caution us that we need to consider carefully whether we want to continue to depend on a system in which questions of life and death depend on them.

In the meantime, far from the drama of the Boston trial doubts about America’s death penalty will continue to grow. Americans will continue to focus attention on the risk of executing the innocent, the adequacy of lawyers in capital cases and the taint of racism in the death penalty system. In spite of Tsarnaev verdict people across the political spectrum will continue in increasing numbers to join with the late U.S. Supreme Court Justice Harry Blackmun in refusing any longer “to tinker with the machinery of death.”