The only holdout among six robbery suspects admitted guilt Tuesday in Penobscot County Superior Court.

George Lawson, 20, of Etna, was the only one of the group responsible for a series of robberies in December to maintain his innocence long enough for his case to go before a grand jury. That panel indicted him last month, and he continued to plead innocent at his arraignment a few days later.

But on Tuesday, he pleaded guilty before Justice Jack O. Smith to three of the four robbery counts against him and to six other charges. He pleaded no contest to a fourth robbery charge. A conspiracy charge and several other charges in unrelated cases were dismissed. The plea agreement contained no sentencing limitation, so Lawson faces up to 150 years in prison when he is sentenced later.

The other five, who arrested along with Lawson in an early-January sweep by local police agencies, pleaded guilty within days of being detained. The six, all between 18 and 22, were implicated to varying degrees in 10 robberies between Orono and Newburgh.

Lawson, who was represented by Perry O’Brian, pleaded guilty to a Dec. 2 robbery at a Citgo service station; a Dec. 13 robbery outside Shaw’s supermarket in Bangor, in which a woman’s purse was snatched; and the Dec. 30 robbery of the manager of the Harborside Restaurant in Brewer as he made a night deposit.

He pleaded no contest to a robbery at the Big Apple convenience store in Orono on Dec. 11.

He also pleaded guilty to burglary of a motor vehicle from which Christmas gifts were stolen on Dec. 22 while the car was parked outside K-Mart in Bangor; theft from Ames department store in Bangor on Dec. 13 and a companion charge of ancillary theft because of prior theft convictions; and burglary and theft on July 5 from Speedway 95, and a companion charge of ancillary theft.

Also arrested in the case were Erick Hamlin, 20, of Bangor; Edward Williams, 18, of Brewer; Hank A. Allard, 22, of Levant; Michael T. Scott and James R. Walker, both 18 and from Carmel. All are awaiting sentencing.