Unfortunately, no.
That is not possible I am afraid. It does not record your journey in any way, so there is no way to show (after the fact) what speed you were doing.
Besides, even if it was possible, such data could be tampered with. It would be no more reliable/believable than if you wrote down the speed you were doing on a piece of paper. Any sane judge would give that as much credit, i.e.: none.
However, there may be other ways. Police frequently determine the speed you were traveling by examining skid marks and impact damage. Also, I know that some cars have a 'blackbox' data recorder that records a variety of information that is retrievable after an accident. You would have to check with your car manufacturer.