Lawyers for the singer R. Kelly are asking the Supreme Court to quash his various child sex convictions because they say the convictions are covered by the statute of limitations, TMZ reports. The singer, who is serving a 20-year sentence for producing child sex abuse images and inducing minors to have sex, argued at his original trial that since the offenses occurred in the 1990s, it was too late to try him. Prosecutors successfully countered that a 2003 law known as the PROTECT Act meant sex offenders could be tried at any point. TMZ says his lawyers, who have already had a federal appeal rejected by a Chicago court, are arguing that since the 2003 law had not been passed at the time of his crimes, and does not include a specific retroactive clause, the statute of limitations should still apply. The outlet reports that the high court would decide in the next few months whether to hear his appeal.