On the one hand, Roomey Khan's assistance as a cooperating witness was "extremely substantial." On the other, she seems to have told between 1 and 100 lies to government officials.

Roomy Khan, a former Intel marketing employee and self-employed trader, admitted to engaging in insider trading when she began cooperating with the government in November 2007, federal prosecutors in Manhattan said in court papers filed late Friday. She provided prosecutors with information that eventually allowed the government to secretly record phone calls made by hedge-fund manager Raj Rajaratnam, prosecutors said. Mr. Rajaratnam, the founder of Galleon Group, and Rajat Gupta, his alleged inside source at Goldman Sachs Group Inc., are the two highest-profile persons convicted of insider-trading charges in the government's ongoing probe—in part because of information provided by Ms. Khan, prosecutors said. However, she also told a series of lies to Federal Bureau of Investigation agents and prosecutors about her own criminal conduct and the conduct of others, alerted alleged co-conspirators to the government's investigation and even lied under oath in 2009 in a lawsuit brought by her housekeeper..."Despite the benefits derived from Khan's cooperation, however, Khan also engaged in a course of conduct that threatened to undermine her cooperation and her value as a cooperating witness," Assistant U.S. Attorney Christopher L. LaVigne said.

Witness's Credibility at Issue in Insider Probe [WSJ]