It’s been nearly 50 years since former Green Beret surgeon Jeffrey MacDonald’s wife and two daughters were brutally murdered at their Fort Bragg, North Carolina, home.
MacDonald claimed that on that 1970 night, four intruders killed his wife, Colette, 26, and daughters Kimberley, 5, and Kristen, 2. But MacDonald was convicted of the murders.
He has maintained his innocence, and on Jan. 26, an appeals court in Richmond, Virginia, will hear oral arguments on his “actual innocence” claim, a legal term that sets a high bar for exonerations.
The case is the focus of the upcoming People Magazine Investigates episode “The Accused,” which airs Monday at 10 p.m. ET on Investigation Discovery.
• For more on the Jeffrey MacDonald case, watch “The Accused” on our 10-part true crime show, People Magazine Investigates, airing Monday night at 10 p.m. ET on Investigation Discovery.
Here are five things to know about the case that has captivated the nation for nearly 50 years:
1. Military Police Did Not Photograph MacDonald’s Injuries
MacDonald’s head injuries were such that a doctor feared he had a concussion. He also had numerous small stab and puncture wounds across his body and a partially collapsed lung. He spent nine days in the intensive care unit.
2. MacDonald’s Pajama Bottoms Were Thrown Away at the Hospital
MacDonald’s pajama bottoms could have yielded clues about what happened. His wallet was also stolen as were two rings from his wife’s jewelry box.
3. Army Hearing Had Once Exonerated MacDonald
After the Army charged MacDonald with the murders in May 1970, it held a six-week long Article 32 hearing (similar to a civilian preliminary hearing) with more than 70 witnesses.
That October, Col. Warren Rock, who presided over the hearing, issued a report exonerating MacDonald and urging civilian authorities to investigate Helena Stoeckley, a troubled drug addict and narcotics informant for Fayetteville, North Carolina, police who had told police and friends she was at the MacDonald home that night. Her boyfriend, Greg Mitchell, confessed repeatedly through the years as well. Both have since died.
4. Prosecutor Cited ‘Total Lack of Evidence’ on Motive
The U.S. attorney general declined to pursue criminal charges against MacDonald as late as Dec. 21, 1973. At the time, he stated, “The exculpatory character of some of the evidence together with the total lack of evidence as to possible motive, in our judgment, are major obstacles to a successful criminal prosecution,” according to a copy of his letter obtained by PEOPLE.
• Watch the People Magazine Investigates After Show, on the new People/Entertainment Weekly Network (PEN). Go to PEOPLE.com/PEN, or download the PEN app on Apple TV, Roku Players, Amazon Fire TV, Xumo, Chromecast, iOS and Android devices
However, intense lobbying by Freddy Kassab, Colette’s stepfather, later helped lead to murder charges being filed against MacDonald.
5. New Evidence in MacDonald’s Appeal
Jeff’s second wife, Kathryn, 55, a longtime family friend whom he married in 2002, became a paralegal to help him with his case and started a website in 2000 that has yielded some of the new evidence that is part of his appeal.
WATCH: Exclusive clip from People Magazine Investigates: “The Accused”