Prosecutors stand by forensic analyses by their experts that identify an indicted FBI agent as the only one who could have fired a bullet that punctured the roof of the truck driven by Oregon standoff spokesman Robert "LaVoy'' Finicum on Jan. 26, 2016.

They argue the work is reliable, relevant and should be admitted at the trial of agent W. Joseph Astarita.

"Each of the government's experts is qualified in his or her respective field, each employed reliable scientific techniques and knowledge in an appropriate manner, and each reached reliable and highly relevant conclusions,'' Assistant U.S. Attorney Paul Maloney wrote in a new court filing Wednesday.

The government alleges that Astarita fired at Finicum as he emerged from his pickup with his hands up after slamming into a snowbank to avoid a police roadblock on U.S. 395. One bullet went through the truck's roof and the other went astray, investigators said. Finicum was among an armed group that took over the Malheur National Wildlife Refuge headquarters near Burns three weeks earlier.

Astarita, a member of the FBI's elite Hostage Rescue Team, has pleaded not guilty to three federal counts of making a false statement and two counts of obstruction of justice. He is accused of hiding from Oregon investigators that he fired his rifle and lying to the FBI about his shots.

Astarita's lawyers have taken issue with the government's five expert witnesses.

Deschutes County sheriff's Deputy Kevin Turpen created a scaled, computer-assisted diagram based on measurements he took at the scene of the shooting. Oregon State Police forensic scientist Victoria Dickerson used trajectory rods to determine the path of the bullet that struck Finicum's truck.

The others worked to identify who fired the bullet based on synchronizing the audio and video taken by Finicum's rear seat passenger Shawna Cox and an aerial video from an FBI plane.

"Determining when in the Cox video the two unaccounted-for shots occurred, then linking that moment with the FBI video and the government's ballistics analysis, will allow the jury to determine who was in a position to fire those two rounds,'' Maloney wrote. "That goes to the very crux of this prosecution - that defendant was the only person who could have fired those two shots.''

Astarita's lawyers contend the government's investigation is based on faulty forensic conclusions, or "junk science.'' They've argued in court papers that the prosecution's 3D animation of the shooting is based on a "a daisy chain of so-called experts'' and not on witnesses, video or ballistic evidence. They've asked the court not to allow the experts to testify at trial.

Prosecutors said defense lawyers can cross-examine their experts at trial, but they should be allowed to present their findings to a jury.

"This court is not tasked with deciding whether a particular expert is right or wrong, 'just whether his testimony has substance such that it would be helpful to a jury,''' Maloney wrote, quoting from case law.

Both sides will make arguments May 21 before U.S. District Judge Robert E. Jones.

Maloney acknowledged that the synchronization of the Cox video with the FBI video didn't match up with one done by the FBI, as defense lawyers have pointed out.

"But that is because the FBI's synchronization is not accurate. It was done very quickly with a very short turnaround time, and was not a final, finished product,'' Maloney wrote. The one the FBI did was used to brief the FBI's top managers, and not intended for forensic use in a courtroom, he added.

Included as a footnote in their latest court filing, prosecutors said the government has offered to pay to have Ryan Bundy, who also was in Finicum's truck, undergo surgery to remove a metal fragment lodged in his shoulder since that day.

Ryan Bundy has told The Oregonian/OregonLive that he believes it's a bullet, adding, "if they want it, they can buy it from me.''

"Notwithstanding public pronouncements of his willingness to cooperate with the collection of this important evidence, Ryan Bundy has refused multiple requests that he consent to undergo surgery (at the government's expense) in order to remove the metal fragment from his body, unless the government meets a number of outrageous demands,'' Maloney wrote " The government cannot compel his compliance.''

Finicum, a rancher from Arizona, died at the scene that day as authorities arrested leaders of the refuge occupation. Oregon State Police troopers shot Finicum three times after he walked away from his pickup and reached for his inner jacket pocket, where police later said he had a loaded 9mm handgun.

-- Maxine Bernstein

mbernstein@oregonian.com

503-221-8212

@maxoregonian