SAVANNAH, Ga. (AP) — Prosecutors never promised immunity from criminal charges to a filmmaker indicted after a crew member was killed by a train while shooting a biographical movie about singer Gregg Allman, the district attorney said in a court filing.

Hillary Schwartz was working as an assistant director on the ill-fated "Midnight Rider" movie Feb. 20 when a freight train slammed into the crew on a railroad bridge in rural Wayne County in southeast Georgia. Camera assistant Sarah Jones, 27, was killed and six others were injured. Authorities say the filmmakers went onto the tracks despite having been denied permission by the railroad.

Schwartz was among four people charged with involuntary manslaughter and trespassing. Last month, her attorneys ask a judge to dismiss the charges. The said Schwartz had been promised immunity from prosecution in exchange for agreeing to a July 29 interview with investigators and prosecutors, who later sought an indictment in spite of their deal.

In a written response to the court, District Attorney Jackie Johnson denied breaking any deals. She said Schwartz was promised only "that nothing she said in the interview would be used against her." Though Schwartz at the time was merely considered a witness, Johnson said, prosecutors sought an indictment after her account of the crash didn't match those of other witnesses and evidence gathered by police.

"Schwartz has offered nothing even remotely to suggest that the state took unfair advantage of her," Johnson said in a court filing last Friday. "She was at all times represented by counsel. The record contains no evidence of a government promise not to prosecute her."

Schwartz's attorney, Austin Catts, did not immediately return a phone message seeking comment Wednesday. He has argued in writing that prosecuting Schwartz after her interview with authorities violates her constitutional right against self-incrimination.

Johnson noted that granting a witness true legal immunity from prosecution requires approval by a judge. She said no such request was made or granted in Schwartz's case.

A March 9 trial has tentatively been scheduled for Schwartz and her co-defendants — director Randall Miller, his wife and business partner, Jody Savin, and executive producer Jay Sedrish.

Involuntary manslaughter is a felony carrying a maximum penalty of 10 years in prison. Criminal trespass is a misdemeanor punishable by no more than a year in prison.

Production on "Midnight Rider," based on the life of the Allman Brothers Band singer, was halted after the train collision.