After a brief review of the "6,000-year search for a truth test," the discussion turns to the relationship between a person's blood pressure and a person's use of deception, noting that blood pressure reliably elevates significantly at the time deception is knowingly used by the subject. After discussing the scientific testing of the lie detector, court responses to the use of lie detector results are addressed, with attention to the Frye case and the legal objection of self-incrimination raised in the Hauptmann case. The application of the lie detector to practical affairs considers its use by prosecutors and police, businesses and banks, and lovers and spouses anxious to resolve uncertainties about truth in their relationships. Also discussed is a relatively new use of the lie detector at the time of this book's writing, i.e., use by psychologists in psychological evaluations. Practical suggestions on lie-detector administration techniques are offered in the concluding chapter. In a concluding comment, Marston notes that no single individual lie detector test is infallible, since it relies upon the skills and judgments of its administrator. A series of tests which reinforce and confirm one another's results, however, are believed by Marston to produce an infallible judgment about deception on specific issues.