I found John Wayne Gacy's brain under study:
The shrunken, sliced brain of serial killer John Wayne Gacy has been preserved in a Ziploc bag since his execution 15 years ago.
www.wmbfnews.com
It was preserved and was no longer its initial dimensions, but the brain morphology was still there. However, at the time of its dissection, science didn't have the powerful techniques it has now for looking deep into the neurons, so it wasn't very helpful.
Scientists use the next best thing (S.P.E.C.T. analysis, which is a kind of MRI). And there, we do find differences between serial killers (usually in prison for life or on death row, they consent to these studies) and the rest of us.
Ted Bundy's brain was given over for study, but I can't find anything scholarly published about it (or in reputable newspapers, for that matter). If anyone finds anything, please post. What they did find, of course, was that MRI and other brain scans showed an abnormal brain (it's probably the physiology as much as the anatomy and things like S.P.E.C.T. can help figure that out - we didn't have S.P.E.C.T. back then, but there were CAT-Scans and maybe MRI's (not sure).
Here's an article on what the scanning data seem to show:
The shrunken, sliced brain of serial killer John Wayne Gacy has been preserved in a Ziploc bag since his execution 15 years ago.
www.wmbfnews.com
The actual academic literature on this topic just gets bigger every year. Right pre-frontal cortex, hippocampus and the amygdala all seem to operate differently in the convicted killers (and for the last two structures, the differences are very small on gross examination, but show up when the brain is in action).