The death penalty should be the ultimate deterrent. After all, if you were to be put to death after committing a crime, surely you would think seriously before committing such a crime. But the deterrent effect of the death penalty is questionable, and if it were an effective deterrent, Texas should have the lowest violent crime rate of any state.
The federal death penalty is even more difficult to analyze. Only in the last few decades, has there been a federal death penalty that applies to general crimes.
Sadly, this apparently came to be in the arms race mentality of the crime control laws of the 1990s, where "tough on crime" Republicans drove Democrats to become equally shrill in demanding ever more severe penalties in fear that they would be labeled in election advertising as "soft on crime." Willie Horton, anyone?
Timothy McVeigh was the last federal prisoner who saw a sentence of death carried out and his killing did little to deter numerous crimes that have followed.
A federal death penalty also allows for a death sentence for those convicted in non-death penalty states by the federalizing of many traditional state law crimes.
With a substantial number of states no longer having the death penalty, and there is a growing and vigorous debate over the methods used to kill those sentenced, there has been a significant degradation in the consensus that once existed on this topic.
Just this week, Nebraska's legislature, hardly a bastion of bleeding-heart liberals, voted overwhelmingly to end the state's death penalty. While a veto is expected, an override is also likely.
The imposition of the penalty on the Boston Marathon bomber, seems little more than continued exercise of cynical political theater.
Source: thenation.com, "What’s Wrong With the Federal Death Penalty," Bruce Shapiro, May 19, 2015