He can be deemed to ill to attend trial. But as long as he is alive, there will be a trial, unless he pleads guilty or no contest, then they will go on to the sentencing part.
If you had cancer and were really sick from chemo and then they told you they could do nothing more and you would die in the next ten months, then you went out and murdered someone, would you still be held accountable? Yes. It has to go on the books as far as the judicial system is concerned.
The family of the deceased will have a better case in a civil suit against the nursing home or the old man if there has already been a criminal case against the old man.
The only way they cannot convict you is if you are already dead.
Then they go after who ever they think they can get for being liable.
We are part of a vengeful society here in the states.
