At risk of getting too gruesome, let’s use a stabbing to illustrate autopsy limitations. Imagine a police officer finds a body in an alleyway and the person has been stabbed about 20 times. Wounds found on the arms and hands indicate that the person was raising their arms to act in self-defense, as sites like Relentless Defense explain. Also, the high number of stab wounds might indicate that the crime was sex-related (i.e., jealousy, revenge, etc.), per the Journal of Forensic and Legal Medicine. That, however, is more of a deduction and belongs to the realm of criminal psychology. And how about the order of the wounds? Which one was first, second, third, fourth, etc.? Unless one particular wound connects to the presence of lots of blood — which a detective at the scene would have seen, not a coroner — there’s no way an autopsy could answer such questions. 

As for toxicological reports, Forensic Science Simplified explains both their complexities and limitations as related to autopsies. Because of the gap in time between death and autopsy, chemicals move around and the body breaks down. The liver, for example, might display the presence of drugs when none actually exist. The stomach can be a more reliable location for gathering information because its contents have yet to be processed by the intestines, bladder, etc., but such findings aren’t foolproof. Hair, bones, and vitreous humor in eyes can also provide toxicological data — but require highly skillful interpretation.