But two,

that they didn't have really any detailed research framework.

They chatted to 20 or 30 serial killers and a few serial rapists and built up some ideas around that.

But they didn't have a background in systematic scientific behavioural research.

What you need to do is to collect information about what goes on in crimes and collect information about the people who've committed those crimes and see how they relate to each other.

It turns out not to be as tidy and simple a framework as fictional detectives would have you believe.

In the years since, behavioral analysis and investigative psychology, a related field that David spearheaded, have done systematic behavioral research to figure out the relationships between crime scenes, behavior, and perpetrators, which has helped them develop new strategies for hunting down suspects.

But to put the label profiling on them adds this sort of mythology of insights and getting into the mind of the criminal and having some sort of magic.