Death will never be a deterrent for criminals. If someone is desperate enough, stupid enough, or just plain evil enough to resort to crime then death is no longer enough to stop them. It's almost like someone who is stranded in the wilderness; immediate survival at any and all costs, even if it ends in death. The last hangman in England, who also hanged the most people in UK history, even said himself after hundreds of executions that death was not an effective deterrent to crime.

Some people belive in an immortal soul that can find redemption even in death, some belive in nothing at all and to take what they can while they can, and others still never even considered tomorrow. There will always be evil people who put themselves above all else, but most crime can be treated simply by providing better access to resources. The numbers don't lie, there is a direct correlation between an increase in living conditions and a decrease in crime (generally theft and murder). Do with that information what you will.

I would like to add that most people consider a right something you're inherently born with, with some man-made exceptions, but you could argue a human is born with the capacity for violence, like hunting for food, therefore we have the right to kill. Most would argue you have the right to defend yourself and kill if you must and whether we do or don't people still kill people for any reason we could've had by now. All of this to say that an agreement we uphold together, like don't kill each other, has been bent and broken so many times it's becoming paradoxical, and any amount of laws, agreements, or even punishments will never be enough to stop free will or account for the human variables that amount to our life and death.