Tutankhamun's mummy
Detective Michael R. King and FBI profiler Gregory M. Cooper came together with an actual Egyptologist to form their own theory which was that Tutankhamun was murdered. With the use of forensic evidence and their extensive backgrounds in criminology, they came to the conclusion that he was likely murdered by one of his closest advisors, Ay. Ay did succeed Tutankhamun on the throne, so they used that as the motivation for the murder.
Tutankhamun's mummy
Christine El Mahdy, an Egyptologist, argues that Tutankhamun died of natural causes, which she believes was most likely a tumor of some sort. She uses the original assumption from Carter's examination that Tutankhamun had a quick burial ceremony since some elements of the mummification appeared rushed, as proof that he needed to be buried quickly following his unexpected death because the man who was next in line for the throne wanted to avoid a power struggle that might have occurred if the burial process had taken too long. By speeding up the burial ceremony, the new pharaoh maintained order in Egypt.