The impact of SCOTUS's heightened scrutiny in capital cases

I have been kvetching a lot, most recently in posts here and here, about the Supreme Court's expenditure of so much time and energy on death penalty cases when there is so much post-Blakely and post-Booker work to be done.  Nevertheless, spurred by this interesting and insightful commentary by Andrew Cohen about criminal cases in the Term just ended, I should note that the Supreme Court's work in the capital arena seems to be having an impact on the administration of capital punishment. 

Cohen's commentary effectively spotlights "that there's a majority on the court no longer willing to wait for lower courts or state legislators or Congress to ensure more fairness and accuracy in capital cases in particular."  And Cohen reasonably links the Court's recent capital work to modern concerns about innocent persons getting sentencing to death:

These decisions are some of the practical consequences of the concerns Justice Sandra Day O'Connor raised in a speech four years ago when she said: "If statistics are any indication, the system may well be allowing some innocent defendants to be executed.... Serious questions are being raised about whether the death penalty is being fairly administered in this country."

Perhaps even more interesting than these observations are the stories to be found inside the numbers.  As detailed in this post and others linked therein, there are many numerical indicators of recent declines in the use of the death penalty in the United States.  Though the work of SCOTUS surely does not account for all these declines, the Court's heightened scrutiny in capital cases likely does account in part for why so many executions have recently been stayed and also surely in part explains why we are on pace for the fewest execution this year since 1996.