Offender profiling

Offender profiling (or criminal profiling), popularized by crime dramas, is the practice of trying to deduce a criminal's characteristics in order to better find that criminal. It is broken down into two types: geographic profiling concerning the logistics of the crime and the profiling of offenders' personal characteristics.

It turns out Cracker is just a cool TV show and offender profiling doesn't actually work very well.

Methodology
"What I try to do with a case is to take in all the evidence I have to work with . . . and then put myself mentally and emotionally in the head of the offender. I try to think as he does. Exactly how this happens, I’m not sure, any more than the novelists such as Tom Harris who’ve consulted me over the years can say exactly how their characters come to life. If there’s a psychic component to this, I won’t run from it."

- John Douglas, famous FBI profiler

FBI profiling currently relies more on intuition than statistically validated information. Moreover, unsound assumptions are frequently made. For instance, traits of incarcerated criminals are assumed to be found in active offenders, and that these traits are static. Geographical profiling assumes that offenders will stick to routines, and choose victims within a "home range." Another prevalent theory is that offenders operate in an area forming a circle around their home.

Accuracy
Studies done on criminal profiling have demonstrated that there is little to no indication that it is effective. Psychologist Ray Hyman has compared it to cold reading. Investigators and profilers will simply shift the vague narrative they've constructed to fit their findings. One notorious example of the accuracy of offender profiling would be the investigation of the Beltway Snipers. Profilers all agreed that the perpetrators were white males, when in fact they were revealed to be black. Additionally, it was assumed that they would be Maryland residents, but this also turned out to not be the case. A survey of forensic psychologists and psychiatrists conducted in 2006 revealed that less than 25% of them viewed profiling as scientifically reliable or valid.

On the plus side, psychologists constructing a profile of a criminal do tend to average marginally more accurate statements than psychics.