What would happen if A left everything in his will be B and B then killed A. Could B inherit A's estate? Nope. This is an old law as children have been killing parents for centuries as have spouses killing each other. This piece of law is known as 'the forfeiture rule'. There is a recent case, Pike v Pike  QSC 134, where one son was charged with manslaughter of his mother 1 month after she changed her will leaving her entire estate to him. The second son would have missed out, but for the forfeiture rule. This rule was summarised in the case as: http://archive.sclqld.org.au/qjudgment/2015/QSC15-134.pdf It also applies to Joint Tenancies. A and B own a property as joint tenants, A kills B, A would take the whole property because of survivorship. But the law of equity prevents this and converts this into a tenancy in common 50/50. So the murderer A would still be entitled to 50% of the property but the other 50% would belong to the victims estate and pass via the will or intestacy laws.