Donald Marshall, the Canadian man who was convicted of murder in 1971, but acquitted more than a decade later, died early Thursday morning.

He was 55 years old.

The native activist passed away at a hospital in Sydney, N.S. at about 1:30 a.m., his sister Roseanne Sylvester told The Canadian Press

He had been admitted to hospital a few days ago and his family confirmed he was terminally ill. Marshall had gone through a double lung transplant six years ago.

Over the years, Marshall has come to symbolize the fight against wrongful convictions in Canada.

At 17, he was convicted of murder in the death of Sandy Seale, in Sydney, N.S. He spent 11 years in prison on the conviction, before being released in 1982 and eventually acquitted in 1983.

Another man, Roy Ebsary, was eventually convicted of manslaughter in Seale's death.

In the end, a Royal Commission report exonerated Marshall and found that he had been the victim of rampant racism and bad police work.

He eventually received about $200,000 in compensation for his time in prison, and was awarded a monthly stipend for the rest of his life.

Daniel Paul, a native historian, said Marshall will be remembered for many years to come as the man whose long fight against his wrongful conviction led to a major overhaul in the justice systems of Canada and Nova Scotia.

"He fought along with his father right to the bitter end, and they exhonerated him. That was by far the greatest thing he accomplished," Paul told CTV News Channel.

"To that end I think First Nations people in Canada and other people of colour will probably remember him with kindness for many centuries to come."

Fishing controversy

In 1999, the Mi'kmaq man once again made headlines when he won a court battle after being accused of fishing for eels out of season, without a license and for selling them illegally.

The Supreme Court of Canada upheld Marshall's argument that native treaties from the 1760s gave him the right to catch and sell fish, regardless of the season.

However, the highly contentious ruling became a catalyst for a standoff between native and non-native fishermen, after natives interpreted the ruling as giving them the right to fish for lobster out of season.

Non-native lobster fishermen, fearing the depletion of lobster stocks, demanded the federal government put a ban on out-of-season fishing.

The tension came to a head in Burnt Church, N.B. in 1999, when non-native fishermen destroyed hundreds of native traps in Miramichi Bay. After a tense shouting match, equipment and three fish plants were damaged.

The federal government stepped in soon after to help ease the tension and the Supreme Court eventually clarified that federal authorities still had the right to enforce fishing regulations.

Marshall had other legal troubles too. He recently found himself in court over charges of assaulting and threatening his wife, Colleen D'Orsay. He pleaded not guilty to some of the charges.

Health issues

Marshall suffered from chronic obstructive pulmonary disease, which results in potentially fatal breathing problems, usually connected to emphysema or chronic bronchitis.

It was as a result of this condition that Marshall underwent a double lung transplant -- an eight-hour procedure.

He said the surgery was tougher than the other challenges he had faced in his life.

"This was the toughest," Marshall said.

"You know, I went to the Supreme Court of Canada twice and when it came down to challenging myself and my whole life, it was very difficult."

With files from The Canadian Press