A private investigator or private detective is a person who secretly follows and observes persons in public places for the purpose of witnessing behavior and collecting evidence of any illegal or improper activities (photos, videos, etc.). During the divorce process a spouse who suspects their spouse of cheating (adultery) or other improper or illegal behavior may hire a private investigator to follow or “tail” the other spouse.

In Maryland, private investigators are regulated under state law and must be licensed to legally conduct surveillance and investigative work. The Maryland State Police is responsible for licensing private investigators, and applicants must meet certain requirements, including a background check, to obtain a license. When hired during a divorce process, a private investigator may conduct surveillance to gather evidence of adultery or other misconduct that could impact the outcome of the divorce proceedings. However, private investigators must operate within the bounds of the law; they cannot trespass on private property, record conversations without consent of at least one party (Maryland is a two-party consent state for audio recordings), or engage in any other illegal activities. The evidence collected by private investigators can be used in court, provided it was obtained legally and is relevant to the case. It's important for anyone considering hiring a private investigator to consult with an attorney to ensure that the investigation is conducted lawfully and the evidence is admissible in court.