Was listening to Dr. Baden (forensic pathologist) on FNS a little while ago.
He said that an autopsy WOULD show what caused Terri's initial brain injury - if it was trauma caused by abuse it will show it, much as a cut on the hand will result in a scar.
He said that broken bones will show up, that attempted strangulation would show up etc.
The complete autopsy, including reading of all the slides etc may take up to several weeks.
An autopsy may be minimal or it may be exhaustive. They may open the cranial cavity and the body cavities. They don't need to examine every bone, or any bone.