Updated

WASHINGTON -- It's all about sex at the Supreme Court Wednesday when the justices hear arguments in cases involving a national sex offender database and the federal government's appeal of a lower court ruling setting free a man dubbed the S&M Svengali.

The case involving Glenn Marcus (aka the S&M Svengali) has drawn a bit of added interest because now-Justice Sonia Sotomayor was part of the three judge panel in New York that set aside a nine-year prison sentence.

Marcus was convicted of sex trafficking after encouraging women to participate in what the government describes as "violent sexual activity." He posted photos and videos from the encounters on a for-profit Web site called "Slavespace."

Following his conviction, a three judge panel of the Second Circuit U.S. Court of Appeals that included Sotomayor set aside the verdict saying some of the alleged bad acts took place before the 2000 Trafficking Victims Protection Act went into effect.

In her brief to the high court, Solicitor General Elena Kagan says the conviction should be reinstated because Marcus never objected at trial to the admission of evidence presented against him and failed to show any plain error affecting his right to a fair trial.  Kagan notes that then Judge Sotomayor agreed with the decision to overturn the conviction but did so in fealty to Second Circuit precedent.

Sotomayor's concurring opinion cautioned that "where there is no reasonable possibility that an error not objected to at trial had an effect on the judgment, the Supreme Court counsels us against exercising our discretion to notice that error."  Because of her prior involvement in the case, Sotomayor is not expected to take part in this review.

Wednesday's other case looks at a 2006 federal sex offender registration law which requires newly convicted offenders to sign up in an updated national database. In 2007, the Justice Department issued a requirement that people convicted of sex offenses before 2006 also register in the new database.

In 2003, Thomas Carr was convicted in Alabama of improperly touching a 14 year old girl.  He then moved to Indiana where after getting into a fight (with no sexual connection) Carr was arrested and convicted for failing to register under the new law.  He has appealed the conviction claiming the after-the-fact requirement violates the Constitution's Ex Post Facto Clause.