New technologies inevitably raise novel legal questions. This is particularly true of technologies, such as neuro lie detection, that offer new ways to investigate crime. Recently, a number of scholars have asked whether neuro lie detection testing is constitutional. So far, the debate has focused on the Fifth Amendment—specifically whether evidence gathered through neuro lie detection is constitutionally admissible because it is “physical” in nature or inadmissible because it is “testimonial” in nature. Under current Supreme Court doctrine, this Fifth Amendment debate is intractable. However, the more fundamental question of whether the government can compel individuals to undergo a neuro lie detection test does have a clear answer. It just so happens that the answer lies in the Fourth Amendment, not the Fifth. In this Paper, we argue that forcing a criminal defendant, or any other person, to submit to a neuro lie detection test is a substantial invasion of mental privacy that is unconstitutional under the Fourth Amendment.

Volume Number


Issue Number