Defence lawyers at the Conrad Black trial want another chance to question the media mogul's longtime partner David Radler, while it appears Donald Trump will not be used as a star witness.

Lawyers filed a motion on Monday asking the Chicago court "to require the government to produce F. David Radler for examination in the defence case."

Radler, who pleaded guilty to one count of fraud, took the stand last month to testify against Black in exchange for a lenient sentence.

But he told the court he had no idea he would serve his prison term in Canada, and therefore may spend just six months behind bars -- a statement that Black lawyer Eddie Greenspan felt hard to believe, although Radler swore to tell the truth.

Black lawyer Marc Martin filed the motion, which said that Radler "professed ignorance" about "Canadian parole rules governing release of white-collar prisoners after service of one-sixth of a sentence."

The filing also cited evidence Radler consulted with a Canadian parole lawyer before reaching his plea bargain with U.S. prosecutors.

"That Mr. Radler has had the leading Canadian parole lawyer on his legal team since November 2004 is probative of his bias, motive and interest in testifying for the government,'' said the filing.

"It also impeaches his claims of ignorance about Canadian surrender and parole rules."

Meanwhile, Donald Trump never appeared at Black's fraud trial in Chicago, and may never testify.

Hugh Totten, a lawyer with Chicago firm Perkins Coie, said the defence may have decided using the star witness would actually hurt their case.

"There must have been an epidemic of rationality that came in on the defence team, because there was nothing good that Donald Trump was going to do to help this defence," he told CTV News.

Trump remained in New York, although it's unclear why. The celebrity mogul was expected to tell the court about a dinner he attended that was charged to Hollinger International.

Prosecutors have accused Black of abusing company perks and have cited the lavish New York dinner, which cost US$62,869, as an example.

Defence lawyers argue that Trump attended the dinner while negotiating to buy the Chicago Sun-Times building from Hollinger International, making the dinner a business event and thus justifying the costs.

"It is risky because if the jury senses that the defence is playing with their emotions -- that this is just a trophy witness, that you're utilizing and exploiting celebrity to try to fool them -- then it has the opposite effect and it damages Conrad Black," said CTV legal analyst Steven Skurka.

At the heart of the case, Black, 62, and former Hollinger vice presidents John Boultbee and Peter Atkinson are accused of devising a scheme to improperly pocket millions of dollars in fees in exchange for promising not to compete with buyers of Hollinger publications.

Mark Kipnis, a lawyer for Hollinger, is also on trial, accused of facilitating the alleged fraud.

The accused deny any wrongdoing and claim they did properly report any non-compete income.

Black's lawyers are just beginning to lay out their defence after 11 weeks of accusations by prosecutors.

Maclean's editor Ken Whyte, who worked for Black at the National Post, was back on the stand Monday. Black's butler is expected to take the stand after him.

Closing arguments in the case could be heard by June 18, with a possible verdict as soon as July 1.

With a report by CTV's Lisa LaFlamme and files from The Canadian Press