Conrad Black leaves though the front gates of his Palm Beach, Fla., mansion in an SUV on March 3, for the three-hour drive to a Florida prison. He is appealing his conviction. ((Adrian Wyld/Canadian Press))

Lawyers for Conrad Black have appealed his conviction for obstruction and fraud, arguing that U.S. prosecutors failed to prove their case against the former press baron.

The appeal, which was filed in Chicago, contends that the government didn't generate enough evidence to prove Black defrauded anyone or attempted to hide documents.

A jury convicted Black on July 13, 2007 of obstructing justice and defrauding shareholders of his former newspaper company, Hollinger International Inc.

Black entered the Coleman Federal Correction Complex in central Florida on on March 3 to begin serving his 6½-year sentence.

An appeal hearing could begin in June. If the appeal fails, Black will have to complete at least 85 per cent of his sentence before being eligible for parole.