ABSTRACT
In this chapter, the author connects three topical areas to explain why psychological experts may sometimes overstep, proffering what appears to be illegitimate inferences and conclusions in courts in insanity cases. He examines expert psychological testimony in two recent high-profile insanity cases: that of Andrea Pia Yates and that of Lee Boyd Malvo. The author seeks to Erskine’s second theory of insanity, which is an organic theory that embraces the psychological within it, and provides an account of insanity’s origin. He offers some thoughts on illegitimate testimony, given these old and new constraining contexts, and what this augurs for future insanity cases, experts testifying, and the law. Thomas Erskine’s physiological theory attempted to etiologically ground Hadfield’s delusions, motives irresistible, and criminal actions on brain damage. In the psychological theory he proposed, Erskine claimed that the essence of insanity was delusion, a partial insanity, such that a truly insane individual could be deluded at one moment but lucid at another.
