I am Phoenix Wright, an attorney who is considered the best in the world. My current case involves a football player accused of two counts of first degree murder. He had allegedly killed his wife and her lover after discovering them together when returning home. After leading the police on a high speed car chase, he surrendered himself to the authorities.
My client, Mr.{redacted} claims to have been possessed by a demon at the time of the murders, and had been controlled by the malevolent spirit for some time before them. After the murders, the spirit left his body, dumping him with the responsibility while cackling that nobody would believe his story. As he was not in control of his actions, we plan to present this as evidence to the courts.
The existence of demons have been known to the public for some time, as they have occasionally crossed the barrier separating our world from theirs. They manifest in physical forms to wreck havoc on society, only burning into ash after they have sustained significant damage. They are also known to possess living organisms. However, humans that have been killed while being possessed also burn to ash, leaving behind only a blackened stain on the ground. No documented cases exist in which a human survived possession, as they are usually killed in the pursuant conflict with authorities.
An ancient religious text speaks of a part-time carpenter turned messiah who once exorcised a demon called "legion" from the body of a young man. Various other texts speak of exorcisms by holy men to free people from possession. However, in my research both historical and folkloric, I have found no information on how to determine if someone was possessed by a demon after the fact. This would make proving my client innocent rather difficult.
Is there any way to test whether or not a person has been possessed after the evil spirit leaves them in order to exonerate my client?