A historian’s quest for the truth about a gruesome mob lynching of two black couples is prompting a U.S. appeals court to consider whether federal judges can order grand jury records unsealed in decades-old cases with historical significance.

The young black sharecroppers were being driven along a rural road in the summer of 1946 when they were stopped by a white mob beside the Apalachee River, just over 50 miles (80 kilometers) east of Atlanta. The mob dragged them out, led them to the riverbank and shot them multiple times. For months the FBI investigated and more than 100 people reportedly testified before a grand jury, but no one was ever indicted in the deaths of Roger and Dorothy Malcom and George and Mae Murray Dorsey at Moore’s Ford Bridge in Walton County.

Historian Anthony Pitch wrote a book about the killings — The Last Lynching: How a Gruesome Mass Murder Rocked a Small Georgia Town — and continued his research after its 2016 publication. He learned transcripts from the grand jury proceedings, thought to have been destroyed, were stored by the National Archives.

Heeding Pitch’s request, a federal judge in 2017 ordered the records unsealed. But the U.S. Department of Justice appealed, arguing grand jury proceedings are secret and should remain sealed.