It is hard to think that there was ever a time when there were no detectives – after all, there are huge numbers of television programmes, films, and novels which feature them. It is, as well, my own genre!
But, once upon a time, there were only police, or the Watch, or the Bow Street Runners, or forces which, in general, were there to keep the peace and carry off miscreants to jail. It is thought that Edgar Allan Poe was the first to write a detective story, The Murders in the Rue Morgue.
The first real detective department was in Paris, where the Sûreté was established by a man with criminal convictions, who had spent time in prison. Eugene Francois Vidocq, born in Arras in 1775, felt that people who had been criminals would be best at detecting and catching other criminals. So all his early detectives had records! This is not a big jump – police and criminals naturally move in the same circles and this can be used in many techniques of deduction.
Amazingly, Vidocq was responsible for the introduction of many methods of detection, including undercover work (he was a master of disguise), contributions to forensic science (research into the possibility of using fingerprints, ballistics, making the first plaster casts of shoe prints), He is also credited with the introduction of a record keeping system for criminal investigation. He created both indelible ink and unalterable bond paper. His form of anthropometrics is still partially used by French police. He also claimed he never informed on anyone who had stolen out of real need.
When he was dismissed from the Sûreté, among political and other confusion, he founded his own private detective agency (before Mr Pinkerton), still employing convicted criminals. He married 3 times, had no known children, had many mistresses, made and lost a fortune in business, and died at the age of 81 years.