Well, Capetonian, I guess you are living proof that you could send an a badly informed astronaut to the moon and they would still come back thinking it was made of cheese.
I have been inside many jails in many places, and suspect have a much more intimate knowledge of both those environments and their guests than you. That you make the correct point that some prisoners come from enviroments which are worse than the ones they find themselves in during custody, but imply that the prison environment should be made WORSE to to act as a deterrent is breathtaking in its stupidity.
Your lay opinion of the issues flies in the face of reality: Sweden, for example, has rather good conditions for prisoners when compared to the UK. It also has much lower levels of offending and recidivism. No particular conclusion can be drawn from this other than that awful prison conditions (which abound in UK prisons) are not only manifeslty counter-productive with respect to effective rehabilitation, there is also no demonstrable or believable case for them serving the purpose of deterrence.
And not wishing to hijack Chopjock's discussion with you, but let's be clear about a couple of things here: NO-ONE has been killed as a result of a laser being pointed in the crews' eyes. So there cannot be any killers. And even if there were; they would only be murderers if they deliberately set out to kill someone. That is murder. Otherwise they would be charged with manslaughter. Chopjock is right and you are talking rubbish.