A 33-year-old woman who drove to her trial in her silver-toned Cadillac has been convicted of welfare fraud and perjury in what is believed to be the biggest such case ever.

Barbara Jean Williams was found guilty Thursday of 10 counts of welfare fraud and 12 counts of perjury. Another perjury count was dismissed on a technicality. She faces up to eight years in prison.

Williams was accused of bilking Los Angeles County out of $240,000 by using eight fictitious names and collecting welfare for more than 70 children -- including four of her own.

Superior Court Judge Kenneth Gale, who heard the case without a jury at the woman's request, set sentencing for Dec. 28. Williams remains free on $50,000 bail.

Defense attorney Carl Jones rested his case Thursday without calling any witnesses, presenting any evidence or even giving a summation. He was unavailable for comment.

Jones had said during the early stages of the three-day trial that he would appeal any conviction, claiming authorities should have sought restitution from the defendant before formal charges were filed.

But Gale rejected that argument during a pretrial hearing when prosecutor Ronald Wheeler said investigators had made such a request.

Williams surrendered to authorities June 14 after a computer search discovered the fraud. Officials were alerted by an anonymous telephone tip to feed the name of Barbara Jean Thompson, one of Williams' alleged aliases, into the computer.

The computer printout showed a pattern of identical or similar names for the recipients' alleged needy children. Williams was later accused of filing for aid in 10 welfare offices and collecting a total of $239,587 from September 1971 to February 1978.