He signed it — not his technicians. He is the Medical Examiner — associate or other. He is to be held accountable.
And he will be. If Prosecution wins the case, he will get a raise and a promotion to Chief Medical Examiner Associate.
Note that the witness who complained to his bosses about 'inconsistencies' between his initial report and the one they gave to the court, was put on ADMIN LEAVE.
Go along, get promoted. Argue, get demoted or fired. Serino, didn't go along, got demoted.
I'm not arguing against your point (he signed, he's responsible), just saying that there is a pattern of behavior with the witnesses (and their command structure) in this case, and I don't think it will change.