There are various rules concerning the insanity defense and not knowing which rule Hinckley was tried under, I would guess that it would be up to the legal minds of the State to decide if he can or cannot be tried again. "There are different definitions of legal insanity, such as the M'Naghten Rules, the Durham Rule, the American Legal Institute definition, and various miscellaneous provisions (e.g., relating to lack of mens rea)."

When he was tried it was NOT for murder but attempted murder. Now, some number of years later, the victim died but everyone dies. He actually lived to be 73. Would he have died at 73 regardless of whether he was shot or not? Nobody knows that. That the ME came to this conclusion may or may not be important at this late date. Going through the expense of retrying Hinckley just appears to me to be a waste of tax payer dollars for absolutely no reason. Has he been fully released from Prison or is he still just getting days out while still being monitored?