[kenjackson]

Legal and medical definitions of death I’ve seen include the terms “permanent” and/or “irreversible”.

The prisoner being alive would imply that he never actually died, at least not medically or legally.

[bleh123]

I respectfully disagree. There are conflicting provisions under law, but the widely accepted standard is a declaration "by a qualified medical professional"[1]As another comment here helpfully points out, there are scenarios such a person going missing for a legally mandated number of years before being declared legally dead[2]

[1] http://tiny.cc/mbzzfz [2] https://en.wikipedia.org/wiki/Legal_death

[zozbot234]

I don't think this is correct. People have been declared legally dead simply due to being missing for a long time, and there's nothing "permanent" or "irreversible" about being a missing person - sometimes they show up again.

[MereInterest]

There is a big difference between being dead and being declared dead. One is a fact about the universe, and the other is a fact about what somebody said about the universe. Seeing somebody who was dead and is now alive is cause to start a religion. Seeing somebody who was declared dead and is now alive is cause to doubt that initial declaration.