Coincidentally, I just came home from my class on serial murder.

As to whether or not a serial killer would make a good profiler...I suppose you could say that some of them profile their victims, in a way. It's also not impossible to fake psychiatric/psychological tests. So I suppose if a serial killer could figure out the right responses...

Random Trivia: apparently the Criminal Minds character Jason Gideon was based on John Douglas. John E. Douglas - Wikipedia, the free encyclopedia