someone used my email password
 

I'm a first timer so I don't even know the right questions yet much less the answers. Someone let me know if I'm looking in the right place. A person lived at my home and had my son's passwords. She later moved and impersonating my son used that password to write some vulgar, threatening emails to herself that got him a warning from her attorney. The first time it happened it was AOL that they both used. We then changed the passwords. (A little late I now understand, but we had no idea at the time that such things could be done or that she would do them.) She then accessed another hometown ISP that we hardly ever used and wrote even worse emails that got him arrested in another state. The whole thing was a ploy to keep him from seeing his new son anymore and to tie up his custody case. It did that well enough. It has dragged out almost two years. What we need to be able to do is prove it (inexpensivly). Help!