Does anyone really do consulting detective in real life?

The consulting detective in Sherlock refers to the detective who will be consulted only if the police can't solve it, that is to say, there is no criminal investigation consultant. I think there must be criminal investigation consultants in reality, but they are not compiled. Usually, they are criminal investigation consultants of vagrants, which generally do not exist, because the details of the case under investigation cannot be disclosed to the public. If they are ordinary detectives, there are also simple detectives who consult for the people, mainly to undertake marital affairs and so on, and occasionally there are powerful ones. The police may also consult such a detective for a certain question, but they will not let him waltz in and out of the crime scene.