One Somali pirate convicted of killing four Americans aboard a yacht claims he was abducted and coerced into joining the mission. Another says the United States illegally reached into Somalia's territorial waters to arrest him.

Lawyers for the two pirates argued those points Thursday to a seemingly skeptical three-judge panel of the 4th U.S. Circuit Court of Appeals, which is expected to rule in several weeks.

Abukar Osman Beyle and Shani Nurani Shiekh Abrar were each convicted of 26 charges and sentenced to 21 life terms for their roles in the February 2011 attack off the coast of Africa. They were among 19 men who boarded the 58-foot yacht in hopes of taking the Americans back to Somalia and holding them for millions of dollars in ransom. The plan fell apart when the U.S. Navy intervened.

Yacht owners Jean and Scott Adam of Marina del Rey, Calif., and their friends, Bob Riggle and Phyllis Macay of Seattle, were shot to death. Four pirates also died.

Abrar's attorney, James S. Ellenson, said his client was improperly prevented from presenting evidence that he was invited aboard the pirates' vessel to do mechanical work before being forced to join in the attempted abduction of the Americans. Ellenson said he was unable to find two witnesses in Somalia who, according to Abrar, could corroborate his story.

Judge Dennis Shedd questioned whether those witnesses really existed. Assistant U.S. Attorney Benjamin L. Hatch said there was no evidence they did.

"There are many places in the world today where it would be easy to say 'I have witnesses' and the U.S. can't go there," Hatch said.

Judge J. Harvie Wilkinson III also challenged Ellenson's assertion that the jury did not find that Abrar fired any shots. The judge said other pirates testified that Abrar operated a grenade launcher.

While Abrar is asking the court to dismiss the entire indictment, Beyle is challenging only his murder and firearms convictions — not the piracy counts. His attorney, Lawrence W. Woodward Jr., said that while the yacht was overtaken in international waters about 900 miles off the coast, the killings occurred well within a 200-mile zone that Somalia claims as territorial waters.

Wilkinson said international law imposes a 12-mile limit on territorial waters.

"If we say America doesn't have jurisdiction within 200 miles when its citizens are being slaughtered, that's a staggering holding," Wilkinson said.

Shedd suggested allowing Somalia to set its own territorial limit would set a dangerous precedent.

"Why wouldn't a pirate kingdom assert jurisdiction over every drop of water on the face of the Earth?" he said.