Virginia ? Less than three weeks after his arrest, the boyfriend of the accused “cell phone bandit” admitted in court Thursday that he helped plan and pull off four bank robberies in northern Virginia.

Dave C. Williams, 19, of Fairfax, pleaded guilty to conspiracy and weapons charges. Williams admitted helping Candice R. Martinez rob four Wachovia Bank branches from Oct. 12 to Nov. 4.

Martinez, also 19, was arrested Nov. 15, just hours after police took Williams into custody. She is suspected of being the woman seen in a surveillance camera videotape talking on a cell phone while calmly robbing a bank.

Williams has admitted being on the phone with Martinez throughout all four robberies and driving the getaway car. He also admitted that a note demanding money was written by the couple and produced on his personal computer and printer. Prosecutors said the note threatened to shoot the teller or someone nearby if money was not surrendered.

According to federal prosecutors, Wachovia Bank was targeted because Williams once worked for the Vienna branch and was familiar with its internal operations.