In another scheme, Madrid would change bar-code tags on computer equipment in stores in order to pay retailers less than the value of their merchandise. He sometimes manufactured his own price tags, Field said, and a mobile bar-code printer was found in his car. Sometimes the scam was as simple as taking the bar code off a cheap eMachine and putting it on a more expensive Hewlett-Packard computer, Field said.

Madrid pleaded guilty on Friday in Santa Clara superior court. He faces six to 12 years in prison on the various charges. Sentencing is set for Jan. 22.