Hall, who had been free on bond, was arrested Friday on outstanding warrants in Garrard County, a breach of his bond agreement, said U.S. Attorney Ron Walker. Hall appeared at the courthouse shortly before his trial was set to begin Monday afternoon.
His attorney first entered a plea agreement, but moments before jury selection began, Hall said he had decided not to plea.
After the jury was seated, Hall, dressed in a striped denim shirt and jeans, changed his mind again and decided to plead guilty.
He told U.S. Magistrate Judge Jennifer Coffman that he had agreed to help Hays grow marijuana.
Asked if he had helped distribute it, Hall said, "I didn't do no selling."
Coffman asked if he knew that it was going to be sold.
Hall said, "Yes, ma'am."
He told the judge that he used to be addicted to pain pills, but that he no longer took them.
Hall, who has an eighth-grade education, told the judge that he understood that his sentence would be a minimum of 10 years and a maximum of life.
Opening arguments were heard today. Others that were charged in the case, Derek Brummett of Junction City; Alan Grass of Wisconsin; and Dean Heckathorn of Michigan are among those expected to testify.
Brummett is Trena Hays' son and Michael Hays' stepson. All three admitted Friday that they were involved in wrapping up the body of Rusty Marshall, a Danville man, and burying it in Odon, Ind.
Heckathorn, who pleaded guilty in September to helping work the farm, has told the court that he also helped dispose of the body and Marshall's truck.
No one has been charged with Marshall's death, but it is being treated as a homicide.
Frank Hall's estranged wife, Beverly Hall, and David Miller's father, William Miller, have also pleaded guilty to helping on the farm.
They face a minimum of 10 years and a maximum of life.
Michael Hays, Trena Hays and Brummett also face up to five years in prison for concealing Marshall's death. The Hayses agreed in court to forfeit $4 million in property and livestock.
It is unclear how Marshall was connected to the Hayses.
All those who have pleaded guilty will be sentenced on Feb. 26, except Heckathorn and William Beasley, of Lawrenceburg, who pleaded guilty in September.