Easily. Sooner or later someone will come into thier environment or they will come into an environment themselves which will allow them to repeat thier original offense. If they know that they will be spending the rest of thier lives in solitary what reason have they for caring about consequences from repeating the crime of murder??

Solitary would only be effective IF it was truly solitary and no guards every had any contact with them in any way. Both of us know this is not true. I do not nor will not acquiesce to your PoV that guards are placing themselves in that situation and so we have to live with those consequences. I would rather we make those guards lives easier by killing murderers and not allowing them to repeat thier offense.

You still have yet to offer a solution. I have now asked several times.