Various
Jewel101 said: "I think it might be important to mention the fact that the psychologist doesn't going around killing people, he's just the reason they are dead. So I think research on psychology is needed."
Do you mean that people die because of his malpractice or neglect? Or is he trying to manipulate people to do things that will cause them to die or commit suicide (in which case he is probably a serial psychopath regardless of the MO)? Or something else?
Linda Adams said: "For me personally, I don't want to read about women being murdered in extremely horrific ways." Not surprising, 90-something percent of the readership for the serial killer subgenre is male. My ex-wife (a good friend) can't even bring herself to read my serial thriller, even though half the vics are male.
Three Seven said: "You're missing the point, and how you can keep a straight face while telling Jewel to skimp on research is beyond me." It depends a lot on what her character is doing. A synopsis would probably make things much clearer. Unless you're going to go into hibernation for a few years, research is a trade-off, time you spend on research in one area is time you can't spend researching something else.
"And Thomas Harris is not a good model - his psychoanalysis of Lecter and his attempt to portray the full extent of his madness in Hannibal was embarrassingly, book-hurlingly lame."
Agreed, and even worse was his lovey-dovey deal with Clarice, which would be virtually impossible given his pathology. Maybe he'll eat her in the next one.
Nonetheless, Red Dragon still outsells anything else in this subgenre two decades after it was written, largely because of Harris's ability to come up with memorable, multi-dimensional villains, which to this day remains the main shortcoming of the serial thriller realm (partly for the simple reason that, other than their savagery, they are generally pretty boring people). And I don't think this subgenre changes that much, there's not all that much difference between, say, John Sandford's recent work and his work of five or six years ago. So at least regarding the serial thriller, I would disagree with Linda's statement that the genre has changed a lot in the last few years, so any comparisons should be made off modern books only. The Butcher's Theater written by Jonathan Kellerman decades ago still trumps any recent works.
In my own case, I spent a year basically just working on my villain and his ghoulishly droll sense of humor. But even though I spent a lot of that year researching psychopathy, I think there is a point of diminishing returns because beyond a month or two of basics, the field becomes either repetitive or contradictory (what for example explains Dahmer, whose childhood environment appears pretty mundane). On the other hand, if the psychology aspect is in some other way a major plot element, as Linda mentioned, then the research is certainly necessary.