Would a question about "undetected crimes" be considered relevant or control? I'm thinking it's a control question since most people could probably answer yes to having committed an undetected crime.

any other opinions?

Let us consider the question, "Have you ever committed a crime for which you have not been caught?" Here, the scope of the term "crime" is not clearly defined. Technically speaking, jaywalking, public urination, underage drinking, and unauthorized downloading of copyrighted music from the Internet are illegal. This is a "control" question.

However, this question can be transformed from a "control" to a relevant question with a simple change in wording. "Have you ever committed an undetected serious crime?" is a standard relevant question asked by U.S. Secret Service polygraphers in pre-employment screening. During the "pre-test" interview, the examiner carefully explains exactly what crimes the Secret Service considers to be "serious" for the purposes of this question. This list includes murder, robbery, rape, arson, grand larceny, etc. The examiner may note that the question does not include the possession and use of false identification for purposes of underage alcohol consumption, but that it does include the sale of such counterfeit documents. It is not expected that most applicants have committed a serious undetected crime, and the question is not ambiguous. It is a relevant question.