Family members of a terminally ill ex-fugitive, who is serving his sentence in Manitoba in a decades-old drug smuggling case, say they have new information that could persuade authorities to let him go back to the United States to die.

Ian Jackson MacDonald, 73, has been serving a conditional sentence in a Winnipeg nursing home since he pleaded guilty last year to one count of conspiracy to import narcotics, in a case that dates back to 1980.

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Ian 'Whitey' MacDonald, seen in a CBC-TV interview in May, is serving a conditional sentence for drug smuggling that includes 24-hour house arrest in a Winnipeg nursing home. (CBC)

Members of his family have been lobbying Canadian and U.S. justice authorities in recent months to let MacDonald — who has terminal prostate cancer and other medical problems — return to Pennsylvania, where his wife currently lives.

MacDonald has 10 months remaining in his sentence, but doctors have estimated that he only has months to live.

His daughter, Lisa Alexander, announced on Thursday she has found information indicating that her father was a confidential informant for U.S. Customs when he was initially arrested in 1980.

Alexander said she was recently told by U.S. Customs officers that MacDonald should never have been arrested.

"They said that he was very helpful, and that they actually spoke very highly of him," she told reporters in Winnipeg.

"They made a deal with him, and it's an over 30-year-old case. He sick, he's dying, and I think he needs to go home."

Was a 'reliable' informant

Alexander showed reporters a letter from the U.S. Customs Service, dated March 9, 1979, and addressed to the U.S. Immigration and Naturalization Service.

"Mr. MacDonald is a documented informant for the U.S. Customs Service and has provided reliable information in the area of large scale narcotics smuggling," states the letter.

"His movements in and outside the United States are necessary in the accomplishment of gathering information on narcotics and alien smuggling activities."

It was signed by Michael W. Wewers, who at the time was chief of the U.S. Customs Service's air support branch in Florida.

On Thursday, Wewers told CBC News that MacDonald should be allowed to go home.

"This guy is not going to come back and create some kind of international drug ring. He's got, I don't know, six months or so to live," he said.

Alexander has sent letters to Prime Minister Stephen Harper and Public Safety Minister Vic Toews, as well as to U.S. senators and congress members, asking them to allow her father to live out his remaining days with his wife in Pennsylvania.

Lived on the lam for years

Originally from Winnipeg, MacDonald — who was known as "Big Mac" and "Whitey" — was arrested in Florida in 1980 on a warrant issued by Manitoba police, who suspected he had helped smuggle more than 225 kilograms of marijuana into Canada.

While in custody, he faked a heart attack and was taken to hospital, where he escaped by conning a guard into removing his leg shackles, according to the U.S. Marshals Service.

MacDonald escaped and lived on the lam for many years, until an officer who was assigned to the file in 2009 found information that led investigators to a home in Pennsylvania, where MacDonald and his wife had once lived under fake names.

Officers learned the couple had moved to a town in central Florida, where MacDonald was located and arrested in January 2011 and returned to Manitoba.

After pleading guilty in September 2011, MacDonald received a conditional sentence of two years less a day to be served in the community.

As a condition of his sentence, MacDonald has been under 24-hour house arrest at the Winnipeg nursing home, except in case of medical appointments or emergencies.