Take the trip off the table and examine it carefully. Once you have looked at it from all angles, then make a decision.
Ask yourself if you absolutely have to go. Do you need to go? Some people say that they have to go somewhere or to some event when they don't have to go. They only think that is the case. You don't have to go anywhere you don't want to go unless you are under subpoena to appear and testify at this trial. It doesn't sound as if you are.
Can you go and limit your involvement? Support the family members who attend the trial but don't sit in on the trial? Attend AA meetings during the day as Mecanix suggested. Post on here.
Sit in the trial but leave the courtroom during the medical examiner's testimony. You can wait in the hallway or in the cafeteria if there is one.
The possibilities are limitless and you don't have to go. Honestly. You don't. Once you give yourself permission to say "I don't have to go" even if you later choose to go, you will have less anxiety.