I have a possibility for you.  The renowned forensic specialist and lawyer, Dr. Cyril Wecht, has a service for free.  You write to him and send him info on your son's case, briefly, as you've done here.  Let him know the forensics; send him Joshua's autopsy.  He will, in turn, call you in about 2 days.  You have probably seen Dr. Cyril Wecht on TV.  Here's his email: chwecht@fyi.net.  He will give you an opinion and maybe what you can do legally.  Good luck.  Keep us posted.