[Also in legal news ... national id.]
There are a few issues addressed in this article, including the importance of postconvinction appeals to determine the legitimacy of trial judgments. Though some have direct experience that underlines the fiction of the point, many focus on the trial as the end. Consider a regular episode of Law and Order.
Another factor involved here, and one that arose in the past few years (partially in my posts), can be called "local option" rules. Thus, a recent article underlined the point that the Bush Administration pushed to have a more "one size fits all" policy as to capital decisions, less discretion given to local prosecutors, prosecutors who under Clinton was given more control to respect local opinion on the matter or make strategic moves (including to make deals, save resources) to choose life.
[Btw, political removals of such federal prosecutors from up top is a controversy in the news ... see, e.g., Talking Points Memo.]
This local option kicks in here if it was determined that the death was done on "Indian land." Another sort of local option controversy arose when states did not per our treaty obligations notify the home governments of non-citizens that they were in custody. Given the U.S. is in the distinct minority in allowing the death penalty, the execution of other nations' citizens is also of central concern to those nations.
And, the federal grand jury is an important factor here, especially with a White House that is more centralized. The local DAs in NYC, for instance, are elected, and can be affected be local political control more than their federal opposite numbers. So, this added level of security, constitutionally secured (a grand jury has not been determined as a federal constitutional right for state trials), to what cases are even brought to trial is at times potentially quite useful. Consider, e.g., drug crimes.
Anyway, interesting article, and one hidden in the middle of the paper, and not accessible by many free of charge even on the NYT site.