Arizona man Donald Day Jr, 60, was arrested by FBI agents in December 2023 and charged with making threats to public figures and law enforcement agents and with illegal firearms possession in the US.

Day entered pleas of not guilty to all charges in the Arizona District Court in May 2024.

Day allegedly sent messages about a “Christian end-of-days ideology” known as premillennialism to the members of the Train family in Queensland between May 2021 and December 2022.

Brothers Nathaniel, 46, and Gareth Train, 47, used high-powered rifles during an ambush to kill Constables Matthew Arnold, 26, and Rachel McCrow, 29, at a remote property at Wieambilla west of Brisbane, on December 12, 2022.

Nathaniel Train joined Gareth and his sibling’s wife Stacey, 45, to fatally shoot neighbour Alan Dare, 58, soon after killing the two constables.

Day’s lawyer Jon Sands filed a pre-trial motion in the US District Court of Arizona earlier in March asking certain evidence be found inadmissible, including testimony from eight Queensland police officers put forward by the prosecution.

“Carefully controlling the admissibility of evidence about the Trains and the shooting — acts for which Mr Day bears no responsibility — is the only way to ensure that Mr Day receives a fair trial,” Sands said in his motion.

All three Trains were shot dead by specialist police officers hours after the ambush in December 2022 when they refused to negotiate or surrender.

Sands accused Australian authorities of targeting Day for actions and speech legal in the US because all the actual suspects were dead.

“The court should limit the evidence admitted about the Wieambilla shooting to a stipulated statement of facts,” Sands said.

“This approach … provides all the context necessary for the government to prove its case, without requiring the emotionally charged testimony of Australian law enforcement officials.”

A coronial inquest into the shootings in 2024 heard the Trains had paranoid beliefs including that they were part of a final battle with Satan and police were “demons” who would transform the family into mindless slaves.

Sands said US federal prosecutors would try to claim Day and the Trains had similar isolated lifestyles and anti-government beliefs.

“The government has indicated that it intends to introduce at trial a large volume of evidence related to the Trains and the Wieambilla shooting,” Sands said.

The Queensland Police Service submitted to the US court witness statements from eight officers including from a Counter Terrorism Command security investigator who reviewed the alleged online and social media interactions between the Trains and Day.

The witness statements contained allegations Queensland police used forensic software to hack into iPhones found at the Trains’ property and discovered messages exchanged with Day on video-sharing websites.

Day is due to stand trial in the US District Court in late April.