SPOKANE, Wash. -- New allegations have been raised that former Spokane Police Officer Karl Thompson did not get a fair trial in federal court because of alleged prosecutorial misconduct.

Thompson's attorneys say their client's conviction should be overturned because US attorneys withheld evidence in the case and misled the Grand Jury about Thompson's guilt.

Additionally Grant Fredericks, one of the government's expert witnesses, is saying his analysis of what happened between Thompson and Otto Zehm in a surveillance video from the Zip Trip convenience store was misrepresented in federal court.

Fredericks was first hired by local officials back in 2006 to analyze the video captured during Thompson's altercation with Zehm. Fredericks provided a frame-by-frame review and was supposed to serve as a witness for the prosecution at Thompson's recent trial.

But now he's saying the United States withheld evidence that could have benefited Thompson's defense.

"If a government lawyer hires an expert they might have information from that expert that's not going to be privy to the defendant. So they're obligated if some of that information might suggest innocence, they're obligated to disclose it," Spokane defense attorney Chris Bugbee said.

Fredericks detailed the way federal prosecutors allegedly misrepresented his analysis in this statement filed in federal court. Prosecutors wrote that Fredericks would testify that the officer hit Otto Zehm with a baton almost immediately after entering the Zip Trip. Fredericks however says at least 23 seconds passed before there was any evidence of a strike.

He also said that he was misquoted. When the government alleged the video shows a baton strike knocking Zehm to the ground.

US attorneys say they did make the defense aware of Frederick's exculpatory concerns in a March 1, 2010 FBI report.

"They've also said in their response that not only was the information given to the jury but that information was given to the defendant's attorneys long before the trial," Bugbee said.

Judge Fred Van Sickle is concerned enough about the possibility that evidence was withheld that he's delayed sending Thompson to prison and the defense has motioned for a new trial and perhaps closer than ever before to getting one.

"It's potentially very significant but again we won't know that until there is further discovery," Chris Bugbee explained.

Further discovery won't happen until the court releases Fredericks from a confidentiality agreement he signed with the government.

On Tuesday Judge Van Sickle postponed Thompson's sentencing indefinitely. If he can't get a new trial his attorneys hope to greatly reduce his sentence.

Prosecutors initially felt they could put Thompson behind bars for about eight years but now a pre-sentencing report recommends the veteran officer only serve 27 to 33 months.

Thompson's defense team argues that their client is ready to take responsibility for using excessive force against Zehm while prosecutors say Thompson still feels he didn't do anything wrong and simply trying to spare himself a longer prison term.

RELATED DOCUMENT: Exhibit 3 - Evidence of Grant Fredericks