Jon B Gould and Kenneth S. Leon (American University - School of Public Affairs and George Washington University) have posted A Culture That Is Hard to Defend: Extralegal Factors in Federal Death Penalty Cases (Journal of Criminal Law and Criminology, Vol. 107, No. 4, 2017) on SSRN. Here is the abstract:
At the height of the federal death penalty (1998-2004), there existed a floor of defense resources below which defendants had twice the chance of being sentenced to death at trial. Moreover, the lowest cost defenses had little to do with legal factors and instead reflected political, geographic, and cultural influences. Put another way, there were — and undoubtedly still are — systemic and systematic differences that make the provision of defense resources in federal capital cases arbitrary at best.