"Thought Crimes: The Case of the Cannibal Cop" (2015 release; 88 min.) is a documentary about NY cop Gilberto Valle. As the movie opens, we see Valle participating in a chatroom, having "ugly thoughts" about what he'd to to certain women. We then go back in time as we get to know Valle, a New York cop with a lovely wife and young daughter. When his wife discovers (through spyware) what Valle has been doing while on the computer, she contacts the police, and Valle is arrested for conspiring to kidnap. Did Valle cross the lien between free thought and punishable action? At this point we are 10 min. into the documentary, you'll just have to see for yourself how it all plays out.
Couple of comments: this was the first feature-length documentary from producer-director Erin Lee Carr. I recently watch her more recent work (2017's Mommy Dead and Dearest, and this year's outstanding At the Heart of Gold: Inside the USA Gymnastics Scandal and equally riveting I Love You, Now Die), which establish Carr as one of the country's best documentarians, period. For her debut feature-length, Carr looks at the infamous "Cannibal Cop" case, which presents a tough legal issue: where does one cross the blurry line between free thoughts (you can literally think the most ugly and repulsive thoughts as long as you don't act on it) and punishable actions. It appears that many reviewers here (and of course the jury) are not able to look beyond the ugly and disgusting thoughts of this despicable man. The theme of "thought police" have been explored before, including in "1984" and Steven Spielberg's "Minority Report", but it's once thing to see it in a fictional setting, it is quite another to be confronted with an actual real life scenario. Please note that since this documentary was released in May, 2015,, the US Court of Appeals for the 2nd Circuit ruled on the appeal in December of that year (not going to spoil it, but you can easily look up the court's ruling).
Bottom line: this is not an easy documentary to watch because of the underlying disturbing nature. But it would establish Carr as an up-and-coming true crime documentarian, and her reputation has only grown with subsequent documentaries she has made. Meanwhile, I'd readily suggest you check out "Thought Crimes", be it on VOD or on DVD/Blu-ray, and draw your own conclusion.