Русско-англо-русский юридический словарь

Typically, an unworthy heir is a beneficiary who murdered the testator, is a terrorist group member or has committed a severe criminal offence. In these situations, the court will hold the gift is void, and the named beneficiary will not inherit. (Advisor.ca)

An unworthy heir is usually someone who unlawfully kills another and is a beneficiary of the deceased, and who is prevented from inheriting by the act of unlawful killing. (LexisNexis)