Something to consider is whether he murdered anyone else.It may not have been the first time,may just have been the first time he was caught.There's the possibility he could be a serial killer but you wouldn't know because it's not something he would tell you.I say this because my father was a serial rapist and was only caught and put in prison one time.It didn't mean it was the only rape,just the only time he got caught.

Something else is just because he did his time it doesn't mean he has been rehabilitated.It could just mean that he will be more careful about being caught.My father just went to different states after being released.

And lastly,being in prison for that many years changes a person,they become institutionalized,they have a hard time adapting to life on the outside,the way they have lived in prison,constantly in survival mode doesn't just go away and they resort to the same behavior in stressful times,it becomes their natural instinct.And being mentally ill on top of that,it sure sounds like a dangerous risk to take.

It's your life and you are free to make your own decision but just remember if a man can kill his parents,regardless of the reason,killing a friend,girlfriend,spouse,whatever,would be nothing to him really.And if it was because of his mental illness,there's no guarantee he won't become that ill again.

Good luck with whatever you decide.