Hawaii prosecutors may not proceed with a retrial against Special Agent Christopher Deedy, U.S. District Judge Derrick Watson in Honolulu ruled.
Prosecutors vowed to appeal.
Deedy was in Honolulu providing security for the 2011 Asia-Pacific Economic Cooperation summit. After bar-hopping with friends on his first night in Waikiki, Deedy fatally shot Kollin Elderts during an altercation in a McDonald's.
A 2013 murder trial ended in a hung jury. A second jury in 2014 acquitted him of murder but deadlocked on manslaughter.
Deedy testified at two trials that he was protecting others from the aggressive Elderts. Prosecutors say Deedy was drunk, inexperienced and fueled by warnings from a fellow agent that Hawaii locals are hostile toward federal workers and outsiders.
Watson's ruling directs Hawaii officials to dismiss the case against Deedy and release him from his bail conditions. Watson is putting the dismissal requirement on hold until the all appeals have been addressed.
Conditions have included restrictions on his ability to travel, said Deedy's defense attorney, Thomas Otake. Deedy, who lives in Virginia, is still employed by the State Department but is on desk duty and his police powers have been suspended, Otake said.
Deedy's defense attorneys argued a third trial on manslaughter would violate the double jeopardy clause of the constitution. The Hawaii Supreme Court ruled that a retrial wouldn't violate his double jeopardy rights and Deedy then turned to federal court to stop the state from taking him to trial for a third time.
The clause "protects a person from being 'twice put in jeopardy of life or limb' for the same offense," Watson's ruling explained, citing a court case that says the clause prevents "the injustice our criminal justice system would invite if prosecutors could treat trials as dress rehearsals until they secure the convictions they seek."
"The State accordingly may not proceed with Deedy's October 2018 retrial on reckless manslaughter or any included offenses without violating constitutional prohibitions," Watson's ruling said.
The Honolulu Prosecuting Attorney's office said the case involved the unjustified killing of Elderts.
"It is our moral and ethical obligation to pursue all legal remedies," the office said in a statement.
Dr. Kalamaokaaina Niheu, a spokeswoman for the Elderts family, said they are still processing the ruling. She and fellow members of the group, Justice for Kollin Elderts, held a news conference outside downtown Honolulu's Iolani Palace.
Prosecutors ignored advice from the Elderts' family to pursue a manslaughter charge in the first trial, Niheu told reporters.
Growing up in Hawaii, people don't expect anyone to be carrying guns, said state Rep. Kaniela Ing, who is running for Congress. Ing, who is also a member of the group, likened the shooting to racially motivated police killings of minorities on the U.S. mainland.
"Deedy himself admitted it was racially charged. He said he was warned about the Hawaiians," Ing said. "You go out ... you get drunk, you kind of get rowdy, somebody calls you out and you fire something back. The worst that could happen is that some people maybe throw a couple punches. It's just not in our culture to carry knives, let alone guns."
This version corrects the year of the second trial. It was in 2014, not 2013.
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