Justice Clarence Thomas' vote was not seriously in doubt when the Supreme Court took up the constitutionality of a ban on an abortion procedure in 2006. But Thomas did not attend the arguments on the issue and, other than a brief announcement that he was sick, his absence has not been explained until now.

Thomas said Thursday that his chair was empty that day in November 2006 because he took a spill the night before.

"I had the wonderful opportunity to fall on my face one night and was not able to make oral argument the following day as a result of it," he said at a hearing of a House appropriations subcommittee on the court's budget for the next year.

Thomas didn't identify the arguments he missed, but court officials said later he was referring to the abortion case. Thomas voted to uphold the federal ban.

The accident came up Thursday as part of an account about how well the court's Web site works and a plea for an extra $800,000 for the site.

Since October 2006, the court has been making argument transcripts available the same day a case is argued.

"In order to stay up to speed on the case and what occurred at oral argument, I simply went to our Web site later that day and it was there," Thomas said.