"Any comparison is irrelevant. If we make a life sentence exactly that, a life sentence behind bars, then they won't reoffend and the innocent man won't be executed."

Even if I granted that solution for recitivism (I don't. Too many life sentences are commuted), By your (the anti-capital punishmnet side's) reconning, the imperfect judicial sustem is inflicting lifetimie torture upon an innocent man. (remember? he's innocent -- that's why we connot put him to death)