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slayer rule

n. (context legal English) A legal doctrine that prevents a murderer from realizing any inheritance from their victim, in effect in most jurisdictions.

Wikipedia
Slayer rule

The slayer rule, in the common law of inheritance, is a doctrine that prohibits inheritance by a person who murders someone from whom he or she stands to inherit (e.g., a murderer does not inherit from parents he or she killed). In calculating inheritance of the decedent's estate, the effect of the slayer rule was that the slayer would be treated as though he or she had predeceased the person who had been murdered, therefore his or her share of the estate would pass to his or her issue.

While convicting someone of the crime of murder requires proof beyond a reasonable doubt, the slayer rule applies to civil law, not criminal law, so it is only necessary to prove the wrongful killing by a preponderance of the evidence, as in a wrongful death claim. This means that even a slayer who is acquitted of the murder in criminal court can still be divested of the inheritance by the civil court administering the estate.