The British should implement the death penalty

[ZenGum]

Forensics can be manipulated, faked, or just dumb-ass screwed up, just like any other form of evidence.

I've been in philosophy seminars where captial punishment was the topic, stats like what you want are often discussed, but it is virtually impossible to get a conclusive finding because you need two societies where all conditions are the same except for captial punishment. Capital punishment and high crime rates are correlated because capital punishment is brought in in reaction to high crime rates.