When trust is lost in a relationship, it could takes years to recover, if ever. In many cases the evidence of adultery is not definitive, so the only way to find out the truth is through polygraph testing.
Polygraph exams are used extensively for relationship issues. This is one area of testing where experience makes a big difference. The wording of test questions is critical to a successful exam, since many words can be interpreted differently by different people.
Fidelity testing is utilized to determine whether one partner has had sexual contact with anyone else besides his/her partner. Other related items may include questions about dating, kissing, contact with "exes," etc.