Well, the death penalty does actually stop THAT person from doing it again. The problem is, the appeals process is so cumbersome and lengthy, you need bean counters for figure out if it's just cheaper to keep them for the rest of their lives. The costs from which almost certainly runs into hundreds of thousands of dollars.
IMHO, my solution is more elegant. "Death row", I believe is solitary confinement. So, why not stick another another equally violent psychopath into the cell, and let nature take its course. I figure the guards don'y really have to push the injured to the prison infirmary as fast as they can.
Here in the US we have an epidemic of 2nd & 3rd generation sociopaths, who kill without remorse or regret, over the stupidest arguments. (As an example, there were 36 shootings oveer last weekend alone, and maybe 2 or more fatalities),
IMO, instead of the parents pissing and moaning to the authorities to remediate the problem, old school justice should prevail, and the parents take responsibly for, and be held accountable for the crimes of their "children".
At the rate this country is going, breeding licenses, mandatory abortions, and sterilizations wouldn't be bad ideas either.
Last week, we had a murder over the sale of a "ghost gun". Hey, maybe the system is working after all.

.
I live in "da hood", and I firmly believe, we should pump as many guns into it as the market will bear.
Philly has had 300 gun murders thus far this year, 90% of which are black on black events.It occurs to to, that perhaps that the BLM crew should take stock of, and remediate the problems within its ranks, instead of selling T-shirts, while looting and burning down businesses, over some lifelong, useless, felon like George Floyd. Yes, officer Chauvin was guilty of murder. He should have been charged as such, and that have been the end of it.
As for the whole "driving while black" nonsense, how many of those stops were of people with no insurance, non registration, suspended drivers licenses, warrants for their arrest, and what have you.
BTW, George Floyd's arrest, addiction, and incarceration records are all available online. Is this turd really who you want as "your poster boy"?