TORONTO -- For Canadians serving time in American prisons, the odds of being allowed to transfer to Canada are akin to winning a lottery, even with a Liberal government that has promised to do more for those detained abroad.

Extensive data obtained by The Canadian Press from several sources -- including Global Affairs Canada, Correctional Service Canada, the U.S. Bureau of Prisons and U.S. Dept. of Justice -- show most Canadians incarcerated south of the border are held in state facilities.

In all, 964 Canadians were imprisoned in the U.S. as of May 18, 2016 -- by far the biggest proportion of Canadians held in foreign prisons. Of those, 420 were held in state facilities and 394 in federal facilities.

However, states, which are generally responsible for prosecuting violent crime, are notoriously reluctant to let them transfer to serve out their sentences in Canada, the data show.

Under the International Transfer of Offenders Act, prisoner transfers from the U.S. to Canada require both state and federal approval. Between 1978 when the deal was negotiated and 2014, U.S. federal authorities allowed 1,256 Canadians to return to Canada.

The states, however, allowed just 161 Canadians to transfer. Florida, for example, which holds the most Canadians among states, allowed just four of them to leave between 2000 and 2010.

"There's a great skepticism on the part of the states that sending someone who has offended against their state laws to a foreign country to serve their sentence is a good idea," says Sylvia Royce, the former head of the prisoner transfer program in the U.S. and now a lawyer in Washington, D.C.

"They're just not in that mindset."

Many Americans see the Canadian system as too soft, given that U.S. criminal justice tends to fall on the "far right side of the spectrum" compared to countries such as Canada, where sentences are "so much more relaxed and humane," Royce said.

Overall, the U.S. turns down more than half of Canadian transfer requests. In the past decade, American authorities approved 803 transfer applications -- 759 federal and 44 state. They denied 867 applications -- 639 federal and 228 state.

Other data show Ottawa approved 253 transfers from Canadian offenders over the past five years only to have 17 of those denied by American authorities. However, the proportion of state denials is likely much higher given that applications may not get as far as receiving Canada's OK without prior state-side approval.

Among states, Florida holds the most Canadians, 97, in its federal and state prisons, while Texas at 90 and Pennsylvania at 85 round out the top three. Global Affairs Canada refused to break out the numbers by state and federal prisons, citing unspecified privacy concerns.

One such case is that of William (Russ) Davies, of Richmond Hill, Ont., who was sentenced to life in Daytona Beach, Fla., for a 1986 murder when he was 18 years old. Canada has previously agreed to take him back. Florida, without giving reasons, has consistently refused to let him go.

Davies, now 48, has a new application in process -- he filed it two years ago -- but there's been no indication this one will be successful.

In an interview, Joseph Daou, the head of Canada's transfer program, said Canada has to respect American jurisdiction when it comes to transfers.

"These decisions are discretionary," Daou says. "It's on a case-by-case scenario."

Nevertheless, Daou said the system was working "very well."

Rachel Smith, who runs the private International Transfer Services in Laguna, Calif., said states often look to see how Canada will deal with an offender before making a transfer decision.

"I think they're stickier because they just want people to serve their sentence," Smith said. "They're just opposed to people transferring."