BISMARCK -- A federal jury on Friday convicted 39-year-old Keith Alexander Graves, also known as Chris Woods, on five counts of sex trafficking by force or coercion, distribution of methamphetamine and possession of methamphetamine.

The jury acquitted Graves on three other sex trafficking charges, as well as a charge that Graves obstructed a federal investigation.

Graves showed little emotion in the courtroom as the clerk of court read the verdicts.

Each sex-trafficking offense carries a mandatory minimum sentence of 15 years, with the possibility of life in prison.

The jury's verdict came on the 10th day of the trial and after more than a day and a half of deliberations.

Graves, who represented himself and maintained his innocence throughout the proceedings, did not contest a federal effort to forfeit a number of items - including a baseball bat, BB gun, multiple cellphones, tablets and an iPad that contained photographic and video evidence of Graves' sexual exploitation of several women - as Graves denied ownership of those items.

Graves was a prominent subject of the documentary "The Overnighters," about Lutheran pastor Jay Reinke, who opened his Williston church as a homeless shelter.

The jury found convincing evidence that Graves possessed and sold methamphetamine while living in Williston and used violence and drug addiction to coerce several women into selling themselves for sex - with Graves keeping the profits.

Those women told the jury during trial that Graves also raped or attempted to rape them on several occasions.

Graves used the website Backpage.com to advertise the sexual services of the women, often posting explicit images and charging as much as $300 an hour for their time.

An employee of Backpage testified at trial that there were more than 500 pages of invoices for ads, which several victim witnesses testified were paid for by Graves.

He was arrested in July 2014 and charged in state court. The case was transferred to the U.S. District Court for North Dakota in December of that year. Graves' arrest was one of the first high-profile human trafficking cases in North Dakota’s Oil Patch.

After accepting the jury's verdict, Judge Daniel Hovland ordered a pre-sentence investigation and tentatively scheduled a sentencing hearing for Feb. 18.

Much as he did before the trial, Hovland cautioned Graves about representation.

"I repeatedly warned you about the dangers of representing yourself," Hovland said. "Please don't be stubborn and try to undertake the sentencing issues yourself."

Hovland said federal sentencing guidelines are complicated and told Graves to avail himself of attorney Thomas Tuntland's legal expertise in preparing his sentence recommendation.

Graves, who has been in custody at Burleigh County Detention Center since late September, asked Hovland to be transferred back to the Heart of American Correctional and Treatment Center in Rugby. He expressed concern about being able to access the legal materials there in time to file a motion for appeal.

Hovland, in turn, expressed concern about a threat made by Joshua Demontigny, an inmate at Heart of America who warned Graves, while on the witness stand, that "me and you should never end up on the same side of the fence."

U.S. marshals on hand in the courtroom said that, wherever Graves ends up being housed prior to sentencing, they will provide him with all his legal materials. Hovland also told Graves that he would extend filing deadlines on Graves' behalf in the event of difficulties.

At the trial's conclusion, lead trial attorney for the U.S. Attorney's Office for North Dakota, Brandi Sasse Russell, acknowledged that the case was stronger for some of the victim witnesses than it was for others. She said that Graves' acquittals would have no impact on the maximum amount of prison time he could receive.