Test based on the principle of suspect's reaction, if he witnesses an event then he behaves in a ceain way is

* Narcoanalysis is a test carried out on a patient or suspect when he/she, after administering truth serum, comes in a sleep like state, and his/her repressed feelings are released. * Truth serum are drugs used in narcoanalysis. Two most common drugs used in narcoanalysis are Sodium amytal, which is also known as amobarbital or amylobarbition, and Sodium Pentothal commonly known as thiopental or thiopentone * Polygraph measures and records physiological actions of human body especially autonomic nervous system while the subject is asked questions relating to the crime and he answers them. * It is based on the principle that autonomic nervous system changes are beyond reasonable control of an individual and hence autonomic nervous system response changes transpires when the subject tries to tell a lie. * Brain mapping measures the P300 evoked potential. In this test the suspect is made to sit in evoked potential recording machine and is shown objects relating to crime scene or is made to hear sounds peaining to crime site. The sensors from his head pick the event related potentials in the form of Brain Mapping only if the person has been at the site of crime. The accuracy of Brain Mapping is almost 100%.