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 Pennsylvania, private investigators or private detectives are regulated under the Private Detective Act of 1953. They are required to be licensed by the county in which they are headquartered, and this licensing process includes a thorough background check, fingerprinting, and sometimes a requirement to post a bond or insurance. When hired during a divorce process to investigate suspicions of adultery or other improper behavior, private investigators must adhere to state and federal laws regarding privacy and surveillance. This means they cannot trespass on private property, wiretap without consent, or engage in any form of illegal activity while gathering evidence. The evidence they collect can potentially be used in court, but it must be obtained legally. It's important to note that Pennsylvania is a no-fault divorce state, which means that evidence of adultery may not be as critical in the divorce proceedings as it would be in states that consider fault when dividing assets or awarding alimony. However, such evidence could still be relevant in disputes over custody or alimony if it can be shown to impact the welfare of children or the economic circumstances of the parties.