crime investgation-truth serum

what is that?-sodium pentathol is used as an investigative aid,which is injected during narco analysis .it is also known as truth serum This is an anaesthetic agent and depending on the concentration of the dose,a person gets into a different level of consciousness.or atrance like condition. inthis state ,a person losese his resistance to the questions that a forsenic expert would put to him. and can a person lie while under the influence of this substance?no a person cannot lie but the answers he gives may or may not be relevent.the skill of the interviewer and the sharpness of his questions also becone relevent.