Lawyers for an FBI agent accused of falsely denying he fired gunshots at Oregon occupation spokesman Robert "LaVoy" Finicum say they've discovered "elemental math mistakes'' that throw into question the government's bullet trajectory identifying the agent as the only possible shooter.

The defense lawyers asked Friday to delay a hearing later this month so they can get a statistician to help them flesh out their challenge.

Prosecutors objected, saying the defense can attack their case at trial.

FBI Agent W. Joseph Astarita has pleaded not guilty to three counts of making a false statement and two counts of obstruction of justice. The government alleges that Astarita fired at Finicum, one of the leaders of the 2016 armed occupation of the Malheur National Wildlife Refuge, as he emerged from his pickup at a roadblock. One bullet went through the truck's roof and the other went astray, investigators said.

Astarita's lawyers said they uncovered "potentially very important statistical errors'' in one of the government expert's analyses, which determined the area where someone had to be standing to fire the bullet that hit the roof of Finicum's truck, using a margin of error of plus or minus 5 degrees.

The defense contends the expert's margin of error was calculated based on mathematical errors.

The government hired Michael Haag, a senior forensic scientist with the Albuquerque, New Mexico, police department, to do a trajectory analysis. He determined the firing spot by figuring out the angle of the bullet as it hit the roof and drawing a line and then extending a cone around the line using a margin of error of plus or minus 5 degrees for the bullet's path.

"If that assumption is wrong, that's potentially a game changer because if that cone opens up, Special Agent Astarita would not be the only agent within that cone,'' defense lawyer David Angeli said. "If those cones are really wrong because of elemental math mistakes, I think all of us want to know that, including the government.''

Angeli told the court that a statistics professor at Northwestern University has indicated a 2008 study Haag used in the analysis that examines margin of error has flawed calculations. The study is described in an article published that year.

He said the defense team needs more time to have the professor study the matter further.

"That cone is the case, really,'' Angeli said.

Assistant U.S. Attorney Gary Sussman argued that the defense wants to hire a statistician to attack the underpinning of a 10-year-old study.

"Everything doesn't hinge on that article,'' he said, arguing that the margin of error has been an industry standard.

Sussman also argued that Haag's bullet trajectory came within 3 degrees of a separate bullet trajectory analysis done by an Oregon state police forensic scientist.

It should be up to a jury, he said, to decide which scientific methods are more credible at a trial that all sides agree will likely come down to a "classic battle of the experts.''

And in any case, Sussman said, the government's case rests on much more than the bullet cone trajectory, though it's an important piece.

Based on video and audio analyses, Astarita is "the only one standing stationary, rifle shouldered, pointing directly'' at Finicum's truck when the shots are fired, Sussman said.

U.S. District Judge Robert E. Jones said the defense can have more time to file supplemental reports with the court on the matter but held firm on the May 21 hearing date.

Government exhibit describing path of bullet that struck roof of Finicum's truck.

Haag's trajectory analysis likely will come under the most scrutiny this month. He used what's called a "rocker point'' method because the bullet that struck the roof of Finicum's truck had only an entry point. That ruled out the usual practice of placing a rod between the entry and exit points.

"Rocker point" refers to an area of indentation at the front of where the bullet impact occurs.

A rod is placed there and then rolled back and forth and side to side until an examiner finds a position where the end of the rod feels "settled'' into the indentation. With the rod held in that position, angle measurements are recorded and back-tracked to estimate the origin.

mbernstein@oregonian.com

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