BILLINGS, Mont. (AP) - Prosecutors have netted a string of guilty pleas among the suspects in an interstate drug trafficking case that's highlighted the criminal underside of an oil boom sweeping the Northern Plains.
The latest to admit to federal charges was Robert Farrell Armstrong of Moses Lake, Wash., described by authorities as the supplier for a large methamphetamine ring that operated in the Bakken oil patch and elsewhere in Montana.
On Wednesday, the 49-year-old Armstrong pleaded guilty to possession of methamphetamine with intent to distribute during an appearance before U.S. District Judge Susan Watters in Billings.
He faces a mandatory minimum of ten years to life in prison and a fine of up to $10 million.
Armstrong, also known as "Dr. Bob," was arrested in October in a crackdown by state, federal and local authorities seeking to curb rising crime rates within once-quiet rural communities along the Montana-North Dakota border.
Nine other defendants are awaiting sentencing after pleading guilty in related cases, and a tenth is scheduled to enter a guilty plea on Feb. 6. Similar cases are pending in North Dakota.
Yet a prosecutor from the Bakken region suggested the arrests have done little to curb an explosion in meth use over the past year, as cheap, high-quality drugs from Mexico flood the market. Valley County Attorney Nickolas Murnion said the well-paid workers drawn to the region's oil fields have become a "magnet for meth dealers."
"With all the publicity about the money to be made in the Bakken, that's become the focus of their market," he said. "It's coming up through Mexico, cartel meth, and it's a lot purer form than the meth people were making a few years ago."
More than 20,000 people have poured into eastern Montana and western North Dakota since oil production began its meteoric rise in 2008. Tens of thousands more are expected in the next several years as the boom continues.
Since 2008, the number of arrests for all categories in Montana counties that fall within the Bakken region soared from 1,676 to more than 3,000 in 2012, according to the Montana Board of Crime Control. That's an increase of almost 80 percent.
Offenses involving drugs, drug paraphernalia and equipment used to make drugs tripled over the same period, from 103 in 2008 to 312 in 2012, according to the crime board.
Similar spikes in crime have been seen in North Dakota, including a July bust that resulted in 22 people being charged in a conspiracy to sell heroin and other drugs on an Indian reservation in the heart of the oil patch.
In Armstrong's case, authorities alleged he obtained wholesale amounts of methamphetamine from Washington state to be distributed through a network of dealers operating across Montana.
Cities and towns where the drug was sold included Sidney, Fairview, Billings, Big Timber, Columbus, Livingston and Bozeman, according to authorities.
Government prosecutors agreed to dismiss additional drug conspiracy and weapons charges against Armstrong in exchange for his admissions, according to a Jan. 3 plea agreement filed by prosecutors.
The government also agreed not to invoke Armstrong's prior felony drug convictions in Washington state during sentencing.
Armstrong's court-appointed attorney, public defender Anthony Gallagher, said such a move would have doubled the mandatory minimum prison sentence faced by his client.
Judge Watters set sentencing in the case for May 28.
(Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)