Folks hire a private investigator to find evidence. Straighforward.
In the divorce arena, I see private investigators retained for three purposes:
1. Prove infidelity. You may have hunch or a gut feeling that your spouse is being unfaithful but nothing more. So you hire a private investigator to conduct surveillance or determine whom an unfamiliar phone number belongs to. But whether cheating is really that important to the outcome of your divorce case is very fact dependent.
2. Uncover hidden assets. A private investigator has access to databases and records that we ordinary people do not. If you have doubts about whether your spouse is disclosing all their assets hiring a private investigator may be worthwhile.
3. Custody/visitation issues. Sometimes a parent has legitimate concerns about the welfare of their child when they are with the other parent. In those instances, they may choose to hire an investigator to provide documentation of substance abuse, the company the parent keeps and other unsafe conditions that their child may be subjected to.
Never hire a private investigator without first discussing it with your divorce lawyer. Your lawyer should be able to advise you on whether a private investigator is really a good investment based on the particular circumstances of your divorce case.