In "Almendarez-Torres v. United States", , Congress's nearly uniform history of treating recidivism as a sentencing factor led the Court to conclude that the aggravating fact there—a prior conviction for certain crimes—was merely a sentencing factor exempt from the jury-trial requirement of the Sixth Amendment. By contrast, Congress has made "serious bodily injury" an element of many crimes, such as assault by a member of the armed forces, ; violence at international airports, ; and genocide, . Furthermore, carjacking is a species of robbery, and hence both Congress and state legislatures have traditionally treated serious bodily injury as an element of a more serious robbery crime.