A man accused of robbing two Lake Tahoe banks in 2010 pleaded guilty to a string of Northern California bank hold-ups Friday.Former Carson City resident David Griffith Osborne, 74, pleaded guilty in federal court in Sacramento to three counts of armed robbery in connection with bank heists in Gridley, Rancho Cordova and Paradise.He will serve just more than 10 years in prison if a judge approves a plea agreement with prosecutors.In the agreement Osborne also admitted to robbing Bank of the West branches in Kings Beach and South Lake Tahoe and two robberies of the same Bank of the West branch in Grass Valley.Osborne is required to pay restitution to each of the six banks as part of the plea agreement. He has also admitted to a robbery of a Carson City Bank of the West in April 2010 and a failed robbery attempt at a Bank of the West in Antioch, Calif. He was not charged in connection with those incidents.Osborne used similar methods during each of the robberies, which took place between December 2009 and June 2010. He wore a fedora, sunglasses, a fake mustache and goatee as a disguise.During the South Lake Tahoe robbery, Osborne entered the bank branch about 4:30 p.m. Feb. 18, 2010, walked to a teller, said “hold up” and put his hand on a silver starter pistol in his waistband, according to court documents. He demanded money and told the teller not to give him a dye pack before leaving the bank with approximately $5,450.Less than a month later, on March 9, Osborne entered the Bank of the West branch in Kings Beach about 3:20 p.m. with the silver starter pistol in his hand and told the teller to empty the drawers. He left the bank with $5,634, according to court documents.Authorities identified Osborne as a suspect in the crimes from surveillance footage and obtaining DNA from a abandoned bicycle used to flee from a Paradise, Calif. robbery in June 2010.An arrest warrant for Osborne was issued in January 2012. At the time, he was serving a three-year sentence in Lompoc Federal Correctional Complex on drug trafficking charges after being stopped in a motor home in Kansas in December 2010 with more than 40 pounds of cocaine and 160 pounds of marijuana.Osborne also has a federal conviction from 1992 for conspiracy to manufacture methamphetamine.He is scheduled to be sentenced on the bank robbery charges March 29.Under sentencing guidelines, Osborne faces a maximum of 25 years in prison for each armed robbery conviction.• The Union reporter Liz Kellar contributed to this report.