If a prisoner on death row has a heart attack or something and is declared legally dead for several minutes and then successfully resuscitated with no magic, would the law set them free? No.

Our medical system has no definitions for undeath or strict, clear-cut resurrection. A person is alive or dead; there’s no “second life”. As such, a resurrected criminal would still be treated as a criminal, and everyone involved with his execution and the handling of his body would be investigated for falsifying documents and assisting with a prisoner escape, until it can be proven that necromancy was involved. If necromancy can be absolutely proven, then it goes to the courts, likely the highest court in whichever country our hypothetical zombie criminal is from.

Odds are, the judges would then side with the spirit of the law, rather than the letter — the death sentence is meant to permanently remove someone from society for a heinous crime. They’d very likely set the precedent that a death sentence means the prisoner stays dead, and future death sentences would make this explicit. Then necromancy would probably be made a severe felony.

In short, people wouldn’t tolerate someone gaming the legal system in this fashion.