New York ? Just days after selling her ImClone stock, Martha Stewart said she knew CEO Sam Waksal had been trying to dump his shares in the company, a close friend of Stewart testified Thursday.

The revelation by Mariana Pasternak, a friend of Stewart for more than 20 years, was perhaps the most damaging testimony yet against Stewart, who claims she sold the stock for an entirely different reason.

Pasternak said Stewart told her about the Waksal sale on Dec. 30, 2001, just three days after Stewart sold her 3,928 shares of ImClone. The pair were on a terrace at a Mexican resort where they were vacationing.

Pasternak said Stewart recalled Waksal “was selling or trying to sell his stock, that his daughter was selling or trying to sell his stock.”

She said Stewart added, “Isn’t it nice to have brokers who tell you those things?”

What Stewart knew about Waksal when she sold her stock goes to the heart of the government’s case that the homemaking mogul repeatedly lied to investigators in the ImClone probe.

Stewart told investigators she never recalled being tipped that Waksal was selling, and that she sold instead because she and her stockbroker had a prior agreement to sell Stewart’s ImClone Systems stock if it fell below $60 a share.

Earlier Thursday, a forensics expert testified broker Peter Bacanovic used a different ink to make a notation next to an entry for ImClone stock on a worksheet of Stewart’s stock sales.

The government contends Bacanovic made the notation after he and Stewart hatched the false $60 story.

The chief forensic scientist at the Secret Service, Larry Stewart, who is considered the nation’s top expert on ink, said infrared and ultraviolet light tests had confirmed differences between the “(at)60” entry and other marks on the sheet.