MIAMI -- A man accused of taking part in the hijacking of the "Joe Cool" charter boat and the killing of its captain and crew will stand trial a second time in January following a mistrial on most of the charges last week, a federal judge decided Monday.

Still uncertain is whether the jury's convictions will stand on four weapons-related counts, which lawyers for Guillermo Zarabozo, 20, contend are inconsistent with the panel's failure to find him guilty of 12 murder, kidnapping, robbery or boat hijacking charges.

"We should start from scratch, because justice hasn't been achieved," said Zarabozo attorney Brian Stekloff. "The jurors misunderstood the law."

U.S. District Judge Paul Huck said he would give prosecutors and the defense additional time to make arguments about the merit of those convictions. Even Huck said it was unusual for a jury to convict someone for use of a firearm in a violent crime, yet be unable to decide if the person actually committed that crime.

"It kind of raises an eyebrow," Huck said.

The new trial for the at least 12 counts Zarabozo faces is scheduled for Jan. 19.

The defense has filed a motion to have the four convictions vacated, and the prosecution will give its reply on Friday.

Zarabozo, a security guard, is accused of participating in the September 2007 hijacking of the "Joe Cool" along with 36-year-old Kirby Archer, an Arkansas fugitive who has already pleaded guilty. Zarabozo testified that Archer shot all four victims using Zarabozo's 9mm handgun and that he wasn't aware of Archer's violent plans.

Slain at sea were the captain, 27-year-old Jake Branam; his wife, 30-year-old Kelley Branam; and crew members Scott Gamble, 35, and Samuel Kairy, 27. Their bodies were never recovered, nor were any weapons, but Zarabozo acknowledged bringing his gun aboard.

Prosecutors said Zarabozo was a willing accomplice and that he committed two of the four killings, but Zarabozo denied that. Zarabozo insisted he brought the gun believing he was going to the Bahamas for a lucrative security job arranged by Archer, who claimed CIA connections.

The "Joe Cool" was ultimately found abandoned and adrift a few miles north of Cuba, which authorities say was Archer's ultimate destination in a bid to escape theft and child molestation investigations in Arkansas. Archer and Zarabozo were found in the boat's life raft.

Jurors were unable to decide if Zarabozo was a direct participant in the crime. They appeared confused about the weapons charges, at one point asking Huck during deliberations to clarify the law, but then decided to convict him on just those counts -- which carry a minimum sentence of 85 years in prison.

Some jurors said in subsequent media interviews they thought the weapons counts were minor and wouldn't have agreed to a guilty verdict if they'd known the magnitude of the possible sentence. Assistant U.S. Attorney Karen Gilbert said Zarabozo shouldn't get another chance on those charges simply because jurors were troubled.

"This scenario is not one where the court should set the verdict aside. We live with it. That's the verdict," she said.