The use of neurobiological evidence in sentencing mitigation.

Neurobiological evidence has grown increasingly relevant in U.S. criminal proceedings, particularly during sentencing. Neuroimaging, such as functional Magnetic Resonance Imaging and Positron Emission Tomography scans, may be introduced by defense counsel to demonstrate brain abnormalities to argue for more lenient sentencing. This practice is common for penalty mitigation in cases eligible for capital punishment. This article reviews the history of the use of neuroscience in criminal cases from the early 20th Century to present, noting pertinent legal and ethical considerations for the use of such evidence. The authors review important empirical research conducted in recent years regarding the use of neurobiological evidence in legal proceedings (such as mock-juror studies) and guidance from the federal sentencing guidelines and the American Bar Association. The discussion also notes relevant case law in which neuroimaging, behavioral genetics, or other neurobiological data were introduced in criminal proceedings, particularly precedent-setting U.S. Supreme Court cases.