A renowned Michigan opera singer and his husband have appeared in a Texas court to face charges of sexually assaulting another man in 2010.

University of Michigan professor and countertenor David Daniels and William Scott Walters each made an initial appearance in a Harris County court Monday and were released on $15,000 bonds. A Harris County District Attorney spokesman says they were ordered to surrender their passports.

Daniels and Walters were arrested in Ann Arbor, Michigan, last month on warrants arising from the criminal complaint of Samuel Schultz. He told The Associated Press the couple drugged and assaulted him when he was living in Houston as a 23-year-old graduate student.

Lawyer Matt Hennessy says his clients are innocent and looking forward to a court hearing on Schultz's "false claims."