Nancy Tullos, former Broadcom human relations chief, pled guilty Tuesday to charges of obstruction of justice. She will also assist the feds in their case against the company.

Broadcom recently corrected its books by some $2.2 billion as a result of the probe, the largest yet of any of the 200 companies now being investigated for stock option backdating.

While the practice is not necessarily against the law, it is illegal for the companies to do it without any kind of notation within their accounting. Internal audits showed that Broadcom had used the practice quite frequently, and upper management was aware of it.

Co-founder Henry Nicholas was one of those executives with responsibility in the practice, although his lawyer said he did not knowingly participate in the backdating. Other executives were found to have culpability as well, and those people are likely the ones the fed hopes Tullos will help to prosecute.

All parties involved refused to comment to the Associated Press on the story as the plea deal has apparently not yet been filed.