Yet another look at the death penalty deterrence question

I just saw on SSRN this paper, titled “Another Look at the Deterrent Effect of Death Penalty.” Here is the abstract:

There is a question whether the execution rate is appropriate to examine the deterrent effect of death penalty.  Instead of using execution rate, this paper uses dummy variables to categorize states into different groups and to compare the group mean homicide rates.  With U.S. state-level panel data for the period 1995-2006, this paper fails to find a significant homicide-reducing effect of death penalty.

Because I lack a deep understanding of statistical methods and social science techniques, I cannot readily assess whether this new paper is a significant contribution to the long-raging debate over the deterrent impact of the death penalty.  I would be grateful to hear from informed commentors about whether and how this latest paper contributes to what we know (and don’t know) about the real-world impact of capital punishment.