A judge on Monday ruled grand jury transcripts from the investigation into the 1946 unsolved murders of two black couples - brutal killings known as America’s last mass lynching - should be released after the efforts of a New Jersey lawyer.

A federal appeals court upheld a lower court decision to unseal the documents, which stem from an FBI probe into the horrific July 1946 murders of Roger and Dorothy Malcom, and George and Mae Murray Dorsey in rural Monroe, Georgia. The decision came from a three-judge panel of the 11th U.S. Circuit Court of Appeals.

The U.S. Department of Justice argued grand jury transcripts are secret, while lawyer Joseph J. Bell Jr., of Bell & Shivas in Rockaway, countered that the historical significance of the files warranted an exception.

“It will shine a bright light on a dark part of American history,” Bell said of the decision Monday.

Bell argued the case after meeting historian Anthony Pitch, who authored a book on the murders called "The Last Lynching: How a Gruesome Mass Murder Rocked a Small Georgia Town.” A judge in 2017 granted a request to release the files, but Justice Department lawyers appealed.

Roger and Dorothy Malcom, along with George and Mae Murray Dorsey, were traveling together by car when they were stopped by a white mob of around 20 to 25 people at the Moore's Ford Bridge. The couples were pulled from the car and shot several times.

“I am at a loss to understand why [the DOJ] would want to keep this confidential,” Bell said of the government’s push to keep the documents under seal.

"Perhaps now the truth of this unfortunate, gruesome act will be finally unearthed and displayed to the world,” Bell told the Associated Press.

In a majority opinion, Circuit Judge Charles Wilson called the lynching “an event of exceptional historical significance.”

"Compared to the journalist or the family member of a victim that seeks access to the details of a salacious unsolved crime, the Moore's Ford Lynching is historically significant because it is closely tied to the national civil rights movement,” Wilson wrote.

More than 70 years later, there were was little risk that possible witnesses could be intimidated or anyone arrested, the opinion noted.

In a dissenting opinion, U.S. District Judge James Graham said he was concerned people still alive today may find their reputations damaged if the transcripts "reveal that their parent or grandparent was a suspect, a witness who equivocated or was uncooperative, a member of the grand jury which refused to indict, or a person whose name was identified as a Klan member."

“I believe that judges should not be so bold as to grant themselves the authority to decide that the historical significance exception should exist and what the criteria should be,” Graham said.

FBI agents investigated the case, leading to multiple possible suspects in a probe that involved interviews with at least 2,700 people. The grand jury, however, failed to indict anyone for crimes. Both the FBI and Georgia Bureau of Investigation has since officially closed the case.

It was not yet clear if the Justice Department would appeal the decision. Lawyers for the DOJ could ask for the matter to be considered by the full bench of the 11th Circuit or take the issue to the U.S. Supreme Court.

This story contains material from The Associated Press

Noah Cohen may be reached at ncohen@njadvancemedia.com. Follow him on Twitter @noahyc. Find NJ.com on Facebook.

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