I know that no criminal justice system is perfect and that even under the standard of proof beyond reasonable doubt, wrongful convictions can occur. That said, I also acknowledge that wrongful convictions under that burden of proof are rare enough that I'd be willing to accept capital punishment for murder, arson, and maybe some other crimes.
One possible solution would be to allow capital punishment for such crimes while still allowing a judge full discretion to waive it in favour of life with hard labour. Most judges would probably opt for the lower punishment by default just so that they can sleep easy at night. However, the knowledge that a judge could impose capital punishment could serve as a deterrent even if judges habitually opt for the lower punishment.
The numbers probably look good till you are one of them.
Having been wrongly convicted and having cost the chief of police his job over it ( while STILL having to buy a pardon for something about to become legal to boot), I can tell you it can happen SO easily...
(from my link)
The study concludes that were all innocent people who were given death sentences to be cleared of their offences, the exoneration rate would rise from the actual rate of those released – 1.6% – to at least 4.1%. That is equivalent in the time frame of the study, 1973 to 2004, of about 340 prisoners – a much larger group than the 138 who were exonerated in the same period
http://www.pnas.org/cgi/doi/10.1073/pnas.1306417111
“This is a disturbing finding,” said Samuel Gross, a law professor at the University of Michigan law school who is the lead author of the research. “There are a large number of people who are sentenced to death, and despite our best efforts some of them have undoubtedly been executed.”
The study concludes chillingly that “the great majority of innocent defendants who are convicted of capital murder in the United States are neither executed nor exonerated. They are sentenced, or resentenced to prison for life, and then forgotten”.