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The 10th U.S. Court of Appeals on Thursday upheld the conviction of a Utah man on a gun charge, ruling he had not shown that an erroneous jury instruction affected the outcome of his trial.

Justus Cornelius Rosemond was one of three people who drove to a Tooele park in August 2007 to sell a pound of marijuana to two men, according to court records. During the transaction, which took place in the sellers' car, one of the would-be buyers grabbed the marijuana and ran without paying. As both men ran, someone in the car fired several shots at them, court records say.

Rosemond was charged with using and carrying a firearm during a drug-trafficking offense; possession of marijuana with intent to distribute; and two counts of being a restricted person in possession of ammunition. Because it was unclear who fired the shots during the failed sale, federal prosecutors tried Rosemond under alternate theories, alleging that he was either the actual shooter or that he aided and abetted the actual shooter's use of the firearm.

At trial in U.S. District Court in Utah, prosecutors told the jury that Rosemond could be convicted of aiding and abetting the crime if he merely knew his accomplice used a firearm in the drug trafficking crime and participated in the offense.

Jurors found Rosemond guilty of all four counts, but the verdict form did not require them to indicate which theory was the basis of the conviction. He was sentenced in March 2011 by Judge Dale Kimball to 14 years in prison.

Rosemond appealed and after the 10th Circuit upheld his conviction, the case went to the U.S. Supreme Court. The high court ruled last year that to convict Rosemond of aiding and abetting, the jury had to find that he had advance knowledge of a firearm's presence, which would show an intent to facilitate an armed drug trafficking crime.

The Supreme Court then sent the case back to the 10th Circuit to determine "the appropriate consequence, if any" of the faulty jury instruction.

In its 3-0 ruling affirming Rosemond's conviction, the 10th Circuit said that when the jurors convicted him of possessing ammunition, "they necessarily found that he was the actual shooter."

"There was no evidence that anyone but the shooter possessed the firearm that contained the ammunition," the ruling said. "Therefore, in convicting Rosemond of possessing the ammunition fired from the gun, jurors had to have found beyond a reasonable doubt that Rosemond fired the gun during the botched drug deal."

—The Associated Press contributed to this story.

Twitter: @PamelaMansonSLC