Private investigators can be used in a myriad of circumstances. The purpose of a private investigator is to have them seek evidence or proof of fact, which has otherwise been unattainable.
Private investigators are trained to find evidence in a manner that avoids detection. They may for example, be able to track an individual to see if they are involved in criminal activity.
A private investigator may also be utilized during divorce proceedings, when one individual suspects that the other is having an affair. Although affairs do not often change the course of a divorce and may not always be applicable as grounds for divorce, proof of the affair can sometimes be helpful in divorce cases.
Private investigators are often used in missing person cases or other cold cases, when law enforcement has been unable to produce a lead.