Dodger - // It might also encourage some of them not to commit murder in the first place. //
Statistics the world over prove that this argument is simply not valid.
I have pointed out, times without number, that no-one commits a murder, or indeed any serious crime, having first considered the consequences - because no criminal ever believes they will be caught.
That's simple human nature - criminals don't rationalise the finer points of the future - especially their own.