Is it necessary to perform all other external, internal, and toxicological examinations on the body, even with such an obvious cause of death? Why or why not?

Question

Scenario: A medical examiner receives a body on which to perform an autopsy. The crime-scene investigator sent a report along with the body that described the crime scene at which the body was found. The man was shot in the head by his disgruntled neighbor, and another neighbor saw it happen. The medical examiner looks at the body and sees an obvious gunshot wound to the head.

Questions to answer: Is it necessary to perform all other external, internal, and toxicological examinations on the body, even with such an obvious cause of death? Why or why not? Provide evidence to support your answer.