SAN FRANCISCO — A former in-house lawyer who’s still fighting stock option backdating charges filed five years ago now claims the Securities and Exchange Commission has mishandled millions of documents.

Attorneys for former Mercury Interactive Corp. general counsel Susan Skaer, one of Silicon Valley’s first in-house lawyers to get caught up in the stock option backdating scandal, on Friday filed a letter claiming the SEC has either lost or destroyed 5 million pages of documents in the case, including more than 500,000 pages of emails to or from the defendants. They want U.S. District Judge William Alsup in San Francisco to impose sanctions.