A US man has admitted to his involvement in a museum robbery, during which he absconded with a pair of ruby red slippers famously worn by Judy Garland's character, Dorothy, in the classic film "The Wizard of Oz."

Terry Jon Martin initially believed that the slippers were adorned with genuine rubies until he encountered a "jewelry fence," an individual involved in the trade of stolen items, who informed him that they were, in fact, made of glass.

Martin's legal representative conveyed to the Associated Press that his client, who is now 76 years old, is dealing with declining health and "confronting his own mortality."

These shoes are part of a rare group of only four authentic pairs that have endured from the 1939 film. Dorothy, the lead character, famously clicked her heels three times while repeating the phrase, "There's no place like home," to return from the Land of Oz to her native Kansas.

The stolen pair, adorned with ruby sequins and glass-bead bows, was among several used by Garland during the production of the musical. In 2005, they were on loan to the Judy Garland Museum in Grand Rapids, Minnesota, the late actress's hometown, from the Hollywood memorabilia collector Michael Shaw.

Martin, who hails from the nearby city of Duluth, forcibly entered the museum through an emergency exit and took the valuable item, insured at $1 million (£824,000), from its plexiglass-encased display pedestal. His motivation for the theft was the belief that the rubies were genuine.

However, when he was informed by an individual involved in the illicit trade of stolen items that the rubies were not authentic, Martin expressed his desire to disassociate himself from the slippers. He disclosed this information to a federal judge during a court hearing on Friday.

The public did not learn of his connection to the crime until 13 years later when the FBI's art crime unit recovered the slippers in a sting operation. This operation was prompted by a man who approached the insurer and offered assistance in recovering the stolen footwear.

Federal prosecutors announced Martin's indictment in May, adding that the current market value of the slippers stood at about $3.5m.

Local media footage showed the thief entering the federal courthouse in Duluth on Friday in a wheelchair, donning a paper mask and carrying an oxygen tank.

Ahead of the hearing, his attorney, Dane DeKrey, told the AP that Martin was in poor health and had been cooperative with him.

"I think Terry is facing his own mortality, and I think when people are reaching that point in their life, they cut through the pleasantries and talk turkey," he said.

Martin - who has a previous conviction, in 1988, for receiving stolen goods - remains free until he is sentenced, although no date has yet been set.

Federal sentencing guidelines recommend eight to 10 years behind bars, his lawyer has said.

Noted