Is this criminal property?

Consider the following:

 i) a person has been convicted of a crime of violence, and imprisoned, (the crime was violence against the person, there was no theft involved),

 ii) he has assets,

iii) the prosecution allege that he also indulged in, shall we say, certain illegal trading activities, but he has never been charged with that,

 iv) the Crown is now pursuing a confiscation order.

If the prosecution have never shown that the assets are wholly or partly the benefits of crime, are they entitled to do this?