In the case of John Cunningham v. California (2006), the U.S. Supreme Court ruled that California's Determinate Sentencing Law violated a defendant's Sixth Amendment right to a jury trial by allowing judges, rather than juries, to make factual findings that could lead to harsher sentences. The court held in a 6-3 decision that any fact which can increase the penalty for a crime beyond its statutory maximum must be submitted to a jury and proven beyond reasonable doubt, as established in previous cases like Apprendi v. New Jersey and Blakely v. Washington. John Cunningham was convicted of sexual abuse charges against his son but received an upper term sentence based on additional factors determined solely by the judge - including vulnerability of victim and violation of trust - not found by the jury or admitted by him during plea agreement. The ruling significantly impacted sentencing procedures in several states with similar laws, requiring them to modify their systems so they comply with constitutional requirements regarding defendants' rights under Sixth Amendment.

In the dissenting opinion for the case of John Cunningham v. California, Justice Alito, joined by Chief Justice Roberts and Justices Kennedy and Breyer, argued that California's sentencing system did not violate the Sixth Amendment. They contended that it was a discretionary system rather than a mandatory one because judges had full authority to select any sentence within each statutory range without additional fact-finding requirements. The dissenters believed this discretion made it fundamentally different from cases like Blakely v. Washington or United States v. Booker where judicial fact-finding increased sentences beyond statutory maximums set by jury-found facts alone; in contrast, they saw no such 'statutory maximum' in California's law since every possible sentence was already authorized by jury verdicts themselves.