Proof beyond a reasonable doubt (PBRD) has long been thought to be fundamental as the standard of proof in criminal cases. Yet PBRD is not expressly mentioned in the Bill of Rights. It was only in 1970 in the juvenile delinquency case In re Winship, 397 U.S. 358 (1970) that the USSC held for the first time that proof beyond a reasonable doubt is a due process constitutional requirement in criminal cases. The court said, "... we explicitly hold that the Due Process Clause protects the accused from conviction except upon proof beyond a reasonable doubt of every fact necessary to constitute the crime with which he is charged." Note again that the USSC was reading PBRD into the Fourteenth Amendment. The opinion held, first, that criminal conviction had to be based on proof beyond a reasonable doubt , and, second, that the same standard applied in delinquency proceedings. See Jackson v. Virginia, 443 U.S. 307 (1979). Failure to instruct the jury on reasonable doubt constitutes structural error that requires reversal; it cannot constitute harmless error. See Sullivan v. Louisiana, 508 U.S. 275 (1993). The USSC has only had one occasion to reverse a case because the definition of reasonable doubt violated due process standards. See Cage v, Louisiana, 498 U.S. 39 (1990). But see Victor v. Nebraska, 511 U.S. 1 (1994) in which the USSC declined to give further guidance in defining reasonable doubt. Here is a list of articles discussing the meaning and usefulness of the reasonable doubt concept. [Author's Note: Since proof beyond a reasonable doubt is a constitutional requirement of due process in all criminal cases, state and federal, shouldn't our U.S. Supreme Court expend whatever resources are available to substantively define this fundamental concept? Do we profit from varying definitions or from leaving it to each juror to come up with his/her own subjective definition? ]