dangrsmind: are you thinking in terms of MPD as the demonic possession defense? I'd like to find some case where this actually worked.
http://www.christian-thinktank.com/eyesopen.html
"...Others found alters that were cold, belligerent, sullen, and 'scary to interview,' and experienced therapists warn that psychiatrists must be wary and can expect violence on the part of the patient when such alters are 'out'. In additions, multiples also experience persecutors who inflict punishment, often in the form of self-mutilation or suicide. The latter is sometimes a criminal, and murderous, evil personality. In other words, the entities appearing in such a person may be kindly, dangerous, or even demonic." [X:NS:HADPE:80f]
"But the contention that the crime was committed while the offender was possessed by a demon keeps cropping up as a defense in criminal court cases. And the literature contains records of a number of famous killers who maintained until the day of their execution that they were innocent of the crimes they had been convicted of and that they had absolutely no memory of having committed any of it. Were the hosts in these instances in fact innocent, and were they killed by the state for the crimes of their alters?"