[JURIST] The US Supreme Court [official website] ruled [opinion, PDF] 5-4 Monday in Peugh v. United States [SCOTUSblog backgrounder] that there is an ex post facto [Cornell LII backgrounder] violation when a defendant is sentenced under US Sentencing Guidelines [materials] promulgated after he committed his criminal acts and the new version provides a higher applicable Guidelines sentencing range than the version in place at the time of the offense. The petitioner in the case, Marvin Peugh, argued that the US Court of Appeals for the Seventh Circuit erred when it used [opinion] the 2009 sentencing guidelines rather than the guidelines that were in place in 1998, the year he committed the crime in question. Justice Sonia Sotomayor delivered the opinion of the court:

The arguments put forward by the Government and the dissent cannot unseat the conclusion that Peugh’s case falls within Calder‘s third category of ex post facto violations. “[T]he Ex Post Facto Clause forbids the [government] to enhance the measure of punishment by altering the substantive ‘formula’ used to calculate the applicable sentencing range.” … That is precisely what the amended Guidelines did here. Doing so created a “significant risk” of a higher sentence for Peugh … and offended “one of the principal interests that the Ex Post Facto Clause was designed to serve, fundamental justice.”

The ruling reversed the Seventh Circuit’s decision, resolving a circuit split.

Justices Ruth Bader Ginsburg, Stephen Breyer and Elena Kagan joined the opinion in full. Justice Anthony Kennedy joined except as to Part III-C, which discussed how the holding “is consistent with basic principles of fairness that animate the Ex Post Facto Clause.” Justice Clarence Thomas filed a dissenting opinion, joined by Chief Justice John Roberts and Justices Antonin Scalia and Samuel Alito as to Parts I and II-C. Alito filed a dissenting opinion, in which Justice Antonin Scalia joined.