Like I said, I'm not sure that's so easy when the victim does not WANT to live. Even in the 24th century, I would expect the patient's will to continue to be a factor as it is today. I think Marritza's spirit would've been long gone even if he could be physically revived--all you'd have would be a brain-dead shell, is my guess.
Perhaps Marritza merely refused care. At the time, he was not a prisoner, and if conscious fully free to make such a choice--assuming medical ethics work the same in the 24th century, which is, I admit, a logical leap.
Likewise, declaring the man mentally incompetent would not have been the hardest task.
Still, I stick by this theory as the best explanation.