During a recent re-watch of this movie, I realized that everyone still refers to Lecter as "Doctor". This is a minor point, but wouldn't he have been stripped of any such titles once the news got out that he'd been, you know, eating people? I can understand Starling and Crawford referring to him as such, but Chilton even introduces him to Senator Martin as "Doctor Hannibal Lecter". You just know that he'd be the first one to stop using the title if it weren't necessary. So what gives?
I see it as a subtle commentary on Lecter's character. He has done things so heinous and ruthless that just hearing about them would make you squirm, yet he is undeniably brilliant and the FBI still has a great deal of respect for him. It's also interesting given the character of Clarice, who is portrayed as sort of a timid but brave interloper in an otherwise male-dominated law enforcement world; perhaps the connotation of "Doctor" also serves to juxtapose her disrespected FBI character against a well-respected cannibal. It's also a constant reminder of the duality of his role in society prior to his capture, and there is a sadistic subtext in the characters referring to the psychotic madman as "Doctor." So I'd say half of it is purely to serve the script and the other half is the characters acknowledging his intellect (especially since much of the movie revolves around them trying to get information and assistance from him).
It's also a way of distancing themselves from him, to keep their conversations as impersonal and formal as possible. They'll call him "Lecter" when he's not present, but when he's actually in the room with them, "Doctor" is a better option, giving away less about their feelings towards him than using his name might.
As long as there was nothing wrong with his thesis, I don't think they can.
Even if his license to practice psychiatry has been revoked, he's still entitled to the honorific.
Chilton introduced him as "Doctor Hannibal Lecter" because he wanted the introduction to be more dramatic. Same goes for the little flourish of his hand. In the novel this is when Senator Martin begins to realize that siding with Chilton was a mistake.
In the novel, Dr. Lecter still writes articles for medical journals while incarcerated.
HOW did Lecter get that pen??? In the film, at least, it seems like the only way he could possibly have grabbed it would be if he used the Force. Which, ya know, is totally legit.
Chilton was careless one day and left it in his cell. This is thoroughly explained in the novel.
During that Red Herring scene where Crawford and his men break down the wrong house looking for Buffalo Bill, why did Crawford look shocked when he mentioned Clarice's name? Did he somehow sense that she found the real home and is in danger or something?
Since Starling is Crawford's prodigy, as well as much more directly involved in the case than he was, he probably figured that she knew where she was. In addition, a previous scene has Starling mention how she knows Buffalo Bill's location, with Crawford retorting he already does. Since Starling was absent when he arrived, he then knew Starling had found the actual location and was already there.
Possibly the result of an Adaptation Explanation Extrication, but how did Lecter manage to remain a free man with a squeaky clean reputation, and a licensed psychiatrist, long enough to later murder the flautist (Raspaill, in the novels) and be "found out" by Will Graham if he had already crippled and disfigured Mason Verger during a therapy session?
IIRC, Verger disfigured himself, due to post-hypnotic suggestion from Lecter. According to The Other Wiki, Lecter treated Verger after the latter's arrest for various crimes, and was himself arrested "soon after" the disfiguring and broken neck. It's likely no one took Verger all that seriously, given his own sick criminal nature, despite his family's money and influence.