DALLAS - A woman whose grandfather shot a home movie of the assassination of President John F. Kennedy in Dallas' Dealey Plaza on Nov. 22, 1963 is suing the US government to either get it back or get $10 million in compensation.

Gayle Nix Jackson filed the lawsuit in federal court on Saturday, a day before the 52nd anniversary of the JFK assassination. Jackson is seeking the original film shot by her deceased grandfather, Orville Nix, or the money.

Jackson's suit claims the film is as important as the assassination footage captured by Abraham Zapruder with his movie camera. The federal government settled with Zapruder's heirs in 1999 to purchase the film for $16 million.

"According to the Warren Commission, the Nix film is nearly as important as the Zapruder film, yet the public is mainly unaware of its significance," the suit states.

The Warren Commission conducted the government's probe of the shooting.

The 8 mm film was taken from the opposite side of the JFK limousine from where the Zapruder film was shot.

Orville Nix sold his film to the UPI news agency for $5,000 in 1963 with an understanding it would be returned after 25 years. During that period, it was turned over to the U.S. government for the Warren Commission and other official probes of the Kennedy assassination, the lawsuit said.

The film was last known to be in possession of the government for the House Select Committee on Assassinations in 1978. Its whereabouts have been unknown ever since, the lawsuit said.

Jackson filed the suit after the National Archives reported to the family this year that the government did not have the original film nor a chain of possession for it, according to her attorney, Athan Tsimpedes of Washington, D.C.

Farris Rookstool III, a former FBI analyst in Dallas, said he helped the family obtain a duplicate of the FBI's copy of the film. The family turned that copy over to the Sixth Floor Museum, the Dallas museum dedicated to JFK's presidency and the assassination.

"The film is a mirror image of the Zapruder film from the other side of Dealey Plaza," Rookstool said.

The film shows a bullet striking the president and first lady Jacqueline Kennedy climbing out of the limo.

Jackson, who has written a book about the film, has been trying to recover the original film for years because she has publicly stated that it could determine whether there was a second gunman involved in the assassination, as conspiracy theorists continue to believe.