The jury is already “death qualified”: That is, only those who said they were open to applying the death penalty were allowed to serve, while those who flatly opposed it were excluded. Many of those who were chosen said they were open to the argument either way. The question now is the degree to which a jury that so thoroughly embraced the government’s case might be inclined to accept the argument that Mr. Tsarnaev’s crimes were so heinous that he deserved to die.