The younger brother of a man serving life in prison for the murder of a 20-year-old Tennessee nursing student pleaded guilty Monday to facilitating her kidnapping and killing.

John Dylan Adams entered a so-called Alford plea, officially maintaining his innocence while acknowledging that prosecutors have enough evidence to convict him of facilitating first-degree murder and aggravated kidnapping in connection with the death of Holly Bobo. He cannot appeal his sentence.

"Our goal when this started was to punish this man as much as we could," Shelby County Assistant District Attorney Paul Hagerman told reporters. "And today, with a guilty plea, John Dylan Adams will serve a 35-year sentence without parole in the Tennessee Department of Correction for his role in this terrible crime."

Adams' brother, Zachary, was convicted this past September of kidnapping, raping and murdering Bobo, who disappeared near her home in rural Parsons, Tenn., in April 2011. Her remains weren't found until September 2014, when they were located by two ginseng hunters in woods not far from their home, about 100 miles southwest of Nashville.

Prosecutors relied on witness testimony to convict Adams after failing to recover useful DNA evidence from Bobo's remains.

HOLLY BOBO'S CONVICTED KILLER SENTENCED TO LIFE PLUS 50 YEARS

Zachary Adams was sentenced to life in prison plus 50 years after reaching an agreement with prosecutors to avoid the death penalty. He is seeking a new trial.

Holly Bobo's mother, Karen, told reporters that John Dylan Adams' plea was "some justice" for her daughter's killing.

"But there is no closure," Karen Bobo added, "and she's still the last thing on my mind when I go to bed every night and the first thing when I wake up every morning."

A Tennessee Bureau of Investigation agent testified at Zachary Adams' trial that the agency made a mistake when it did not pursue leads only days after Bobo went missing that pointed to four men who lived in a dark underworld of crime and drug use: the Adams brothers and their friends Jason Autry and Shayne Austin.

Autry, also charged with Bobo's kidnapping, rape and murder, testified in expectations of getting a lenient sentence and is on a list of witnesses who have been offered immunity. He said the Zachary Adams told him in graphic detail how he, John and Austin raped Bobo. Autry also testified that he served as a lookout while Zachary Adams shot Bobo under a bridge spanning the Tennessee River. Austin committed suicide in Florida in February 2015.

A fellow jail inmate, Shawn Cooper, testified that Zachary Adams told him he was involved in the "Holly Bobo murder case" and wanted him to deliver a message to his younger brother: Stay quiet, or he would "put him in a hole beside her." At the time, Cooper was about to be transferred to the same jail where John Dylan Adams was being held.

Autry, meanwhile, testified that Zachary Adams asked him to kill his younger brother to silence him.

Prosecutors have not publicly revealed the details of John Dylan Adams' involvement, but Shelby County Assistant District Attorney Paul Hagerman did say Monday that he had less involvement than his older brother.

No hearing has been set to resolve Autry's charges, but his lawyer has told the judge that a trial does not need to be set, indicating that he has reached a deal with prosecutors.

The Associated Press contributed to this report.