Southern Union Co. v. United States, 567 U.S. 343 (2012), was a Supreme Court decision that applied the rule set out in Apprendi v. New Jersey—that certain non-conviction elements of a crime must be proved to a jury—to criminal penalties.

[1] Southern Union Company was convicted of storing hazardous liquid mercury without a permit, "on or about September 19, 2002 to October 19, 2004," in violation of the Resource Conservation and Recovery Act.

The Court of Appeals for the First Circuit upheld the sentence, agreeing that the jury had not determined the duration of the violation, but holding that Apprendi did not apply to criminal fines.

[3] The Supreme Court reversed, holding there is no principled distinction between criminal fines and imprisonment for the purpose of Apprendi because Apprendi requires that any fact other than a prior conviction that increases the penalty for a crime beyond the statutory maximum must be submitted to the jury and determined beyond a reasonable doubt.

The rule preserves the historic fact-finding function of the jury, deciding that where a fine is sufficiently substantial to trigger the Sixth Amendment jury-trial guarantee, Apprendi applies.