TORONTO - Conrad Black's request for a new trial or acquittal following his convictions for fraud and obstruction of justice have little chance of success, according to observers who say the Chicago judge is unlikely to overturn the jury's decision after a long and complex trial.

Black's lawyers are asking Judge Amy St. Eve to reverse the jury's guilty convictions or to grant a new trial in a motion filed late Monday with a Chicago court. They cite lack of credible witnesses, prejudicial evidence and faulty jury instructions among their complaints.

But while Black himself said Monday night he was optimistic about his chances, legal experts suggest there's little chance for any of the requests to be granted.

"The odds of success that any of those motions get granted are extremely remote. They're kind of the equivalent of a football Hail Mary pass, hoping that something will stick," said Andrew Stoltmann, a Chicago securities lawyer who has been following the case.

"Judge Amy St. Eve ran a very, very good trial - she let in virtually everything, she really kind of made her decisions kind of appeal-proof."

While the motions like the ones presented by Black's lawyers are quite common ahead of sentencing and appeals, he added, they rarely amount to much since the court system gives a lot of deference to a jury's verdict.

Hugh Totten, a Chicago lawyer with firm Perkins Coie, noted that the filings contained similar arguments used before and during the trial by defence lawyers - also making any sort of favourable result for Black unlikely.

"A lot more things are going to be held to harmless argument in a six-month trial than they are in a six-day trial, just because of the incredible investment that you make when you try a case for (several) months," he said.

"Appellate courts, and judges, are very reluctant to reverse themselves."

In the filings, Black's lawyers took issue with the testimony of David Radler, the prosecution's star witnesses who was also Black's business partner for more than 30 years.

"The only evidence linking Mr. Black to the payments (other than his receipt of a cheque) is the unsupported, incredible testimony of the government's co-operating witness, F. David Radler," the filing said.

"The alleged telephone call on which the government's case rests were undocumented, and even Radler himself could not remember them in detail."

In a separate motion for acquittal, Black's lawyers reasserted their previous claims that the government failed to prove its case beyond a reasonable doubt, and had produced no real evidence the former press baron had attempted to obstruct justice by removing 13 boxes of documents from his Toronto offices despite an Ontario court order sealing the premises.

Defence lawyers for Black's three co-defendants also made similar motions.

Lawyers for Mark Kipnis, a former Hollinger in-house lawyer, called the case a "Greek tragedy" and attempted once again to separate their client from the rest of the accused.

"The record describes a rise to prosperity followed by hubris which, arguably, led to a reversal of fortune. Mark Kipnis was a foil in that play," the court filings stated.

"There are cases in which it is simply beyond the jury's capacity to search through a mountain of evidence, and evaluate that evidence from the very different perspectives of several individual defendants."

The four men were found guilty of three counts of fraud in last month and Black was also convicted of one count of obstruction of justice. The charges related to payments he and other Hollinger executives pocketed from the sale of Hollinger International assets - money prosecutors said belonged to shareholders.

Black, who gave up his Canadian citizenship in 2001 to become a member of Britain's House of Lords, was freed on bail pending sentencing on November 30, but told to stay in Chicago or in Palm Beach, Fla., where he owns a home.

Prosecutors are seeking fees of US$17 million from Black and two of his long-time business associates - Jack Boultbee and Peter Atkinson.

Black faces as much as 30 years in federal prison, and has vowed to appeal.

Peter Henning, a law professor at Wayne State University in Michigan and a former U.S. Securities and Exchange Commission lawyer, said motions to overturn the conviction, get a new trial and stop the forfeiture usually get decided at the time of sentencing or shortly before, unless the judge decides to allow a new trial.

The motions are "a way to preserve the issue for appeal," and often give hints about what defence lawyers will argue when they bring the case the higher Court of Appeal.

"If you don't raise a basis for overturning the conviction at the trial level, then you can be deemed to have waived it. If you win great, if you don't, you have a ruling that you can now appeal."

Most criminal cases involve such requests, with lawyers for Martha Stewart and former Enron Corp. executive Jeffrey Skilling also asking their respective judges for new trials - and being turned down.

Lawyers for Stewart ,who was accused of falsifying stock trading records after she sold shares following a tip from her broker and served jail time after being convicted of obstruction of justice, based their demands on allegations that a juror lied about his arrest record on a questionnaire. Skilling lawyer had argued that evidence presented at the four-month trial was "legally insufficient" to support the convictions.

U.S. prosecutors, who have until Sept. 17 to respond to the defendant's post-trial motions, declined to comment Tuesday.

Black's Canadian lawyer Eddie Greenspan, also declined to comment, saying he could not speak about the filings since they were before the court.