The common term "truth serum" refers to any number of sedative/hypnotic drugs which are used to induce honesty in a subject. In fact, truthfulness is not guaranteed by the use of such drugs; while a person under the influence of a truth serum may become talkative, or may experience reduced inhibitions or even hallucinogenic fantasies, they are still quite capable of lying. For this reason, and the obvious human and civil rights issues (which are similar to those regarding torture), any statements obtained in this manner are inadmissible in court. Or, they're really disgusting concoctions used in crossing the line ceremonies. The best that modern pharmacology can come up with is amobarbital (better known as sodium amytal) and is not all that useful at all.