Appeals lawyers for Martha Stewart (search) accused the government Thursday of improperly withholding evidence that "could have led to an acquittal" in the celebrity homemaker's trial.

The accusation, in a letter to federal prosecutors and the judge who oversaw the trial, came one day before Stewart was to report to a federal prison in West Virginia to begin serving a five-month sentence.

The lawyers said prosecutors should have provided Stewart's legal team with documents that emerged as evidence during the recent perjury trial of ink expert Larry Stewart (search), who testified against Martha Stewart at her trial.

Among the documents is a 2002 memo written by a Secret Service scientist who had tested the ink on a worksheet of Martha Stewart's stock holdings — a key piece of evidence against the homemaking maven and her ex-stockbroker. In the memo, scientist Susan Fortunato wrote that ink in a notation of "(at)60" next to a listing for ImClone Systems Inc. (IMCL) stock was different from "all" other inks on the worksheet.

That contention bolstered the government's case that the broker, Peter Bacanovic (search), had doctored the worksheet by adding the "(at)60" notation to support a cover story for why Martha Stewart sold ImClone stock.

In fact, Fortunato had not tested all the ink on the worksheet. She failed to test a dash mark that appeared next to another stock listing — an omission Martha Stewart's lawyers say "sabotaged" the testing.

"That could have led to an acquittal — if the government had complied with its ... obligations and the jury had been aware of the memo," the letter from the appeals lawyers said.

They said they had made repeated unsuccessful requests to federal prosecutors to obtain the full laboratory file for the document testing, including the 2002 memo.

"The government's crime lab sabotaged the critical testing in an effort to secure her indictment and conviction," the letter said. "That revelation to the jury could have easily led it to conclude that the government overreached in prosecuting Ms. Stewart."

Federal prosecutors in Manhattan had no comment, spokeswoman Megan Gaffney said.

Larry Stewart was acquitted earlier this week of perjury charges. Federal prosecutors had accused him of lying on the witness stand at the Martha Stewart trial, exaggerating the role he played in the testing of the worksheet.

Martha Stewart and Bacanovic, were convicted in March of lying to investigators about why Stewart sold ImClone stock in December 2001, just before the stock price plunged.

Both were allowed to remain free pending appeal. But Stewart has elected to begin serving her time anyway, and must report by 2 p.m. EDT Friday to the minimum-security federal prison in rural Alderson, W.Va.

Stewart's lawyers will ask a federal appeals court later this month to overturn the conviction.