It is a statistical "science"- and very often it can be used to good effect... it can determine 'most probable' characteristics of a criminal.

For instance: serial killers tend to be white males, so statistically if you are looking at finding a serial killer- in GENERAL- it will most be a white male. Of course other details could alter the profile considerably.

I dont know if I would call it a science- it is a tool that uses statistics and educated guesses based on psychology to help narrow down a pool of potential suspects.... having too much faith in it could lead to disasterous consequences. It assumes that the criminal is unaware of the method used to profile him- an educated criminal could USE knowledge of profiling to intentionally lead investigators to self defeating assumptions... Just as some criminals now go out of their way to not leave fingerprints and DNA at a crime scene.

Some profiling techniques- such as complex psychological profiles based on handwriting analysis- are pseudoscience, no better than phrenology, astrology or reading tea leaves... and in my opinion they tell you more about the person doing the analysis, than the person that wrote the sample.