I came across the following sites regarding death penalty statistics.
www.deathpenaltyinfo.org “The Death Penalty Information Center is a non-profit organization serving the media and the public with analysis and information on issues concerning capital punishment. The Center was founded in 1990 and prepares in-depth reports, issues press releases, conducts briefings for journalists, and serves as a resource to those working on this issue. The Center is widely quoted and consulted by all those concerned with the death penalty.”
www.icpsr.umich.edu/NACJD/ – the “ESPY” file is the source for death penalty data from 1608 to 1991.
