In the United States v. Glenn Marcus 2009 case, Glenn Marcus was convicted for sex trafficking and forced labor. The victim, known as "Jodi", was subjected to physical abuse and public humiliation by Marcus who also maintained a website documenting these acts. However, his conviction was challenged on appeal due to an ex post facto issue - some of his crimes were committed before such actions became federal offenses in 2000 under the Trafficking Victims Protection Act (TVPA). The Second Circuit Court of Appeals overturned his conviction stating that it violated the Ex Post Facto Clause of the Constitution because he could have been convicted for conduct that occurred before TVPA's enactment. Upon further review by Supreme Court Justice Sonia Sotomayor, she ruled that while there may be ambiguity regarding when certain offenses took place relative to TVPA’s enactment date; this did not automatically mean all charges should be dismissed but rather only those specifically related to pre-2000 activities.

In the dissenting opinion for United States v. Glenn Marcus, 2009, Justice Sotomayor argued that the majority's decision to uphold Marcus' conviction was flawed due to a lack of consideration for potential prejudice caused by pre-Act conduct. She contended that it was impossible to determine whether or not the jury would have convicted Marcus based solely on his post-Act behavior without speculating about their thought process. Furthermore, she criticized the majority’s reliance on an “overwhelming evidence” standard in assessing harmlessness beyond a reasonable doubt as inconsistent with precedent and potentially misleading in future cases. In her view, this approach could allow convictions even when there is substantial uncertainty over whether a defendant received fair notice of criminality under law at time of alleged misconduct.