spo·li·a·tion /ˌspō-lē-'ā-shən/ n
1: the destruction, alteration, or mutilation of evidence esp. by a party for whom the evidence is damaging
2: alteration or mutilation of an instrument (as a will) by one who is not a party to the instrument
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.