He’d have been convicted—my lay guess is for Murder, while being under the influence of ‘sudden passion’; he just wouldn’t have gotten death. See Texas Criminal Code [section] 19.02.
This doesn’t help us answer the debate question though. For me, to answer it you have to go to the goals of punishment, which I’ve read are: retribution, deterrence, rehabilitation, restoration, and incapacitation. Does the death penalty, in this case, achieve any of those goals vs. a lesser form of punishment?
For retribution, death is harsher than life imprisonment. How much harsher, is difficult to say. Dead is dead, after all, but prison is not a pleasant place to spend the rest of one’s life. Point to the death penalty
Rehabilitation: IMO, neither punishment will serve to rehabilitate him more than he has already. He expresses no remorse, yet is judged not likely to do it again. Is remorse necessary to be considered rehabilitated? Will confining him longer increase the likelihood he will be remorseful? Hard to be remorseful if you’re dead. Point to life imprisonment.
Restoration: Neither punishment will bring the dead victims back to life. Killing the doctor prevents him from doing good works which might monetarily compensate his victims’ heirs or society as a whole. Another point to imprisonment.
Deterrence: A carried out death penalty will absolutely deter the doctor from doing this crime again. It may induce other would-be murderers to not committ similar crimes, if they were to rationally consider the death penalty as part of the range of punishments. But the whole point of Texas’s sudden passion mitigation is that instances like catching your wife in bed with your best friend, short circuit the part of your brain that thinks rationally. I can’t see another murderer in a similar circumstance weighing the potential range of punishments. If there’s no consideration, no evaluation of punishment, how can there be deterrence? Tie.
Incapacitation: Like deterrence above, if he’s executed, he’s definitely not committing murder again. But the OP states that our best experts have indicated that he won’t commit this crime again, regardless of whatever punishment we provide. I guess you could argue that the experts are sometimes wrong, whereas no one outside of a horror movie has been recidivist from the grave. Still, it’s my opinion that in this situation, there’s no effective difference between the two punishments when we consider their incapacitative effect. He’s not going anywhere and he’s not killing anyone else, regardless of which punishment we choose.
Summing it all up, I get two to one for keeping the doctor around, with two ties. The above goals of punishment don’t mention catharsis for both society and the victims and victims’ families and loved ones. (Though, re-reading this, I guess you could fold it into one of the reasons behind retribution.) Should we consider catharsis as a worthy goal of punishment? Would his death, or his continued imprisonment, or that he’s created this lovely achievement of ending cancer to be more cathartic? I’ve read of cases where any of the three could be true. On this board, I think opinions would differ whether imprisonment or execution would be harsher, and therefore more cathartic. Assuming catharsis is related to how much the observer thinks the criminal is suffering.
Me, I’d commute his sentence to something that he would have gotten for a second degree felony, something in the 2-20 year range. But then, on these facts, I’d never have given him a capital murder conviction in the first place. Make him a Jerry Sandusky type, who then killed his victims, and I think your utilitarian calculus changes dramatically. That guy? I’m not sure I’d let live, even if your society loses his promised discovery of a cancer cure.