A person who has been schooled in criminal psychology, which involves a unique and highly trained mind, and a person of great intelligence. Criminal psychology is hard to explain properly, but from my understanding, it is when the criminal psychologist has to try and think like a killer (criminal psychologists are sometimes asked to help police with murders), try and get inside their mind, and try to undterstand why the killer committed the crime in question, so the case can be solved, if the criminal psychologist has been hired by police. This may involve using evidence from the crime as a way to try to get inside the killers mind. Criminal psychology doesn't always determine exactly who the killer is, it does help immensely though to give an idea of the personality of the killer, what he's like, and so on. People who knew the victims of the crimes are often interviewed by police to get any possible leads on who the actual killer is, and suspects may also be interrogated to narrow down any list of people the police might believe committed the crime. This all has to do with the criminal psychologist, because he or she is often the one who has to figure out how the crime happened with the information that is given to him/her, whether it be from an acquaintance of the victim, or a suspect, or crime scene evidence.
Dr. John Davies is a criminal psychologist.
The police have hired a criminal psychologist to help them figure out who the killer is in their latest case.