alienist

noun

Etymology: Borrowed from French aliéniste, from aliéné (“insane”).

1. An expert in mental illness, especially with reference to legal ramifications.

   “‘Are you an alienist?’ I interrupted. ‘Every doctor should be - a little,’ answered that original, imperturbably.”

   “A trial for poisoning means an exhaustive study not only of analytic chemistry, but of practical medicine on the part of all the lawyers in the case, while a plea of insanity requires that, for the time being, the district attorney shall become an alienist, familiar with every aspect of paranoia, dementia praecox, and all other forms of mania.”

2. A psychiatrist.