New York ? A federal judge dealt a blow Friday to the government’s effort to prove that Martha Stewart committed securities fraud when she publicly proclaimed her innocence.

U.S. District Judge Miriam Goldman Cedarbaum blocked any expert testimony on whether investors in Stewart’s homemaking empire would have considered Stewart’s statements important.

The securities fraud count — the most serious against Stewart — accuses her of propping up the stock price of her own company, Martha Stewart Living Omnimedia, by claiming in 2002 that her sale of ImClone Systems stock was proper and that she was cooperating with authorities.

Securities fraud carries a potential 10-year prison term. Each of the four other charges against Stewart carries five years. If convicted on any count, she would probably get much less than the maximum.