Brain-based lie testing methods are still very much in the experimental phase, and it is not yet proven whether there is any method that directly examines the human brain that is suitable for lie testing. Even if a method works, it is necessary to clarify the concerns and doubts that it raises. What would be the procedural and forensic limitations of such a method, and at what stage of criminal proceedings would it be appropriate? There are many questions and doubts, yet there are criminal cases overseas in which some methods considered suitable for lie detection, such as brain fingerprinting, have been used. These attempts were premature, and the method should have been validated before it was tried in a criminal case.