Dylann Roof's friend knew about his plans to shoot black church members during Bible study in Charleston, didn't report it and lied to the FBI after the massacre of nine people, according to an indictment unsealed Friday.

Joey Meek, 21, faces federal charges that, if convicted, could land him in prison for years. But with Roof already in jail facing federal hate crime charges and nine state counts of capital murder, why would there be a case against Meek?

Legal experts say prosecutors likely want him to testify against Roof — testimony that could help show Roof's alleged acts were premeditated and intentional, which are vital to pursuing a death penalty case.

"By having a charge against him (Meek), they have more leverage with him to go ahead and make some sort of plea bargain: You testify. You tell us the truth, and we'll give consideration on the charges or penalty involved," long-time criminal defense attorney Jack Swerling said.

During a hearing in Columbia on Friday, Meek stood before a federal magistrate in handcuffs, shackles and an orange jumpsuit. He answered "yes" to questions about whether he understood the charges of lying to investigators and concealing information and the possible sentences they carry. He pleaded not guilty and his bond was set at $100,000.

Meek hung out with Roof off and on in the weeks before the June 17 shooting at Emanuel African Methodist Episcopal. A day after the shooting, Meek told The Associated Press that Roof had drunkenly complained to him that "blacks were taking over the world" and "someone needed to do something about it for the white race."

Authorities say Meek knew more, writing in the indictment that he knowingly lied to an FBI agent when he said "that he did not know specifics of Dylann Roof's plan to shoot individuals on a Wednesday, during Bible Study, at an AME Church in Charleston, South Carolina."

The indictment does not specify how the government knows Meek was lying.

Meek, of Lexington, also said Roof told him that he used birthday money from his parents to buy a .45-caliber Glock semi-automatic handgun. Meek said he took the gun away from Roof the night of his drunken rant but gave it back when he had sobered up.

Swerling said Meek can help prosecutors prove Roof's state of mind and help show he carefully planned the shootings — an important part of establishing aggravating circumstances in a capital case.

"If somebody makes statements beforehand of what they're going to do and why, particularly because it's racially motivated, that's much more aggravated than someone who's just is in Charleston and decides to walk in there and shoot somebody," he said.

Pete Strom, a former U.S. attorney now in private practice in South Carolina, said he expects the government to aggressively pursue any potential witness who could shed light on Roof's case, possibly offering a plea deal or sentence recommendation in exchange for cooperation.

"This guy obviously was close to Roof and, now that he's charged, in order for him to get any kind of deal, he is going to have to agree to cooperate and most likely pass a polygraph," Strom said. "They're going to want to know if this was a wider conspiracy. If there are more people involved, there are going to be more charges."

Meek's attorney and prosecutors also refused to comment.

If convicted, Meek faces a maximum sentence of five years in prison for lying to investigators. The maximum penalty for concealing information is three years.

Meek's brothers and his girlfriend, Lindsey Fry, sat behind him in court. Meek's mother blew him a kiss as he was led out of the courtroom. She was red-faced and teary eyed as she left. None of them wanted to talk with reporters after the hearing.

Meek is on probation, having pleaded guilty earlier this year to possessing a stolen vehicle, according to Lexington County court records.