As long as we are members of the council of Europe we will not have capital punishment.
He has had access to the public unsupervised since 2017, and carried out some of his creepy behaviour of gifting chocolates to a female supermarket worker before he was granted parole.
His modus operandi for his crimes wasn't building connections but pulling young girls off the street. We don't know if his behaviour reflects him changing his MO or is something more innocent, he is a perverted double murderer but he is also probably a very sad lonely man after spending most of his adult life in jail.
But the conditions of his release mean he doesn't get the benefit of the doubt and that is correct and proper for the protection of the public.
This isn't a failure of the system.
Even if we were able to change the law, there is no chance he would get executed because we can't pass laws that are retroactive.