Emotions are so complex that there really is no way to physically detect liars.
Yet people keep trying to devise instruments to judge stress levels, breathing patterns, perspiration, blood pressure, increased activity in the frontal lobes, and other types of functional brain scanning to distinguish between truth and falsehood.
The polygraph was once considered to be a scientifically dependable method of detecting lies, except that the act of being "polygraphed" creates an enormous amount of stress, and everyone feels guilty about something.
Except for sociopaths lacking a conscience, empathy, or remorse. Consequently, the polygraph is usually used as a prop on the unwary, to squeeze confessions out of suspects. The results themselves are not allowed as evidence in a trial.
Now a voice analyzer has been patented and the inventor, Charles Humble, of the National Institute For Truth Verification, (whatever that is), contends that vocal cords can give you away.
To paraphrase a bit of his lengthy press release: