Photo: The Canadian Press. All rights reserved.

A Capitol Police Hazardous Materials Response Team truck is parked at the Russell Senate Office building on Capitol Hill in Washington (AP Photo/Charles Dharapak)

The man charged with mailing letters with suspected ricin to the president and others was surprised by his arrest and maintains he is innocent, according to his attorney.

Paul Kevin Curtis appeared in a federal courtroom Thursday in Oxford, Miss., wearing shackles and a Johnny Cash T-shirt. His handcuffs were taken off during the brief hearing, and he said little.

His attorney, Chrisi R. McCoy, says Curtis "maintains 100 per cent that he did not do this." She says she knows him and his family and that it is hard for her to believe the charges against him.

McCoy says she has not yet decided whether to seek a hearing to determine if Curtis is mentally competent to stand trial.

If convicted, he could face up to 15 years in prison.

He did not enter a plea on the two charges. The judge said a preliminary hearing and a detention hearing are scheduled for 3 p.m. Friday.