Professor John Mee:

The trouble arises in going to court with discretion. Let us say this terrible thing has happened and the family has to go to court to see by how much they can get the killer's share reduced. It could be 10% or 20%. If it is only 10%, they will feel bad and ask why the reduction was so small given the hideous nature of the crime. The discretion in that context is not a good thing.

The difficulty here is with the Constitution. Joint tenancy is an unusual thing in that rights are mixed up with each other. What one wants to do, and what I would completely support, is to stop any benefit being achieved. There is, however, the complexity of deciding what is a benefit in this situation.