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 Washington State, private investigators are regulated under state law. They must be licensed to legally conduct surveillance and gather information. The Washington State Department of Licensing oversees the issuance of private investigator licenses. To become a licensed private investigator, individuals must meet certain requirements, including training, experience, and passing a background check. When hired during a divorce process, a private investigator can legally follow and observe a person in public places to collect evidence of adultery or other improper behavior. However, they must conduct their activities within the bounds of the law, respecting privacy and avoiding trespassing or other illegal actions. The evidence gathered by private investigators can potentially be used in divorce proceedings, particularly if it pertains to issues of infidelity, which can impact decisions related to alimony or the division of assets, although Washington is a no-fault divorce state and adultery may not necessarily affect the outcome of the divorce.