For nearly a year, six Chinese crew members on a ship that crashed into the San Francisco-Oakland Bay Bridge — creating the bay's worst oil spill in nearly 20 years — have been detained by federal authorities.

The sailors are being held as material witnesses in the crash of the Cosco Busan. The men, including four who are not accused of wrongdoing, are fighting for the right to return to their families in China.

"This is a lengthy detention," said University of Georgia law professor Ronald Carlson, an expert on the material witness law. "These witnesses are being detained humanely. Still, there is that undeniable desire to return home."

The 900-foot cargo ship sideswiped a bridge support in heavy fog, gashing its hull and leaking more than 50,000 gallons of fuel that killed and injured thousands of birds. It was believed to be the biggest San Francisco Bay oil spill since 1988.

Prosecutors want the six to testify in criminal cases against the harbor pilot, John Cota, and the ship's Hong Kong-based operator, Fleet Management Ltd. Both have pleaded not guilty.

Although the men are under arrest as material witnesses, they are not in jail.

Living rent-free in apartments and hotels, they are permitted to roam San Francisco and the surrounding area. They continue to draw their salaries, and each also receives $1,200 per month in witness fees, more than the monthly salary of at least one detained seaman.