James Holmes is mounting an insanity defense for his trial in the 2012 movie-theater killings in Aurora, Colorado. But what connection does that tactic have with the actual medical understanding of mental illness? Today on The Gist, Fordham's Barry Rosenfeld explains the challenge of diagnosing a "guilty mind." For the Spiel, we ask Nate DiMeo to share an episode of his podcast The Memory Palace about Coney Island's Dreamland amusement park, and his approach to revisiting history. Today's sponsor: Stamps.com, where you can buy and print official U.S. postage right from your desk using your own computer and printer. Use the promo code THEGIST to get a no-risk trial and a $110 bonus offer. Join Slate Plus! Members get bonus segments, exclusive member-only podcasts, and more. Sign up for a free trial today at slate.com/gistplus.

Learn more about your ad choices. Visit podcastchoices.com/adchoices