Lawyers for actor Alec Baldwin have filed a fourth motion for a New Mexico court throw out charges of involuntary manslaughter related to the on-set shooting death of the cinematographer Halyna Hutchins in 2021.

Attorneys for Baldwin, who is due to face trial early next month, argue in a new court filing that prosecutors withheld evidence showing that the contemporary Colt .45 revolver he used on the set of the western Rust was damaged at the time of the accident.

Baldwin has claimed that he pulled back the hammer – but not the trigger – when the gun went off accidentally, firing a fatal round into Hutchins. Baldwin’s defense team has argued that the gun was prone to malfunctioning.

Last year, prosecutors dismissed an involuntary manslaughter charge against Baldwin, saying they were informed the gun might have been modified before the shooting and malfunctioned. The charge was later reinstated.

A second analysis of the weapon by ballistics experts relied on replacement parts to reassemble the gun after parts of the pistol Baldwin used were broken during the earlier testing by the FBI when its experts hit the gun with a mallet to see if it would fire erroneously.

In the new motion, reported by Variety, attorneys for the actor accuse prosecutor Kari Morrissey of improperly withholding an expert’s report showing “unexplained toolmarks” on the gun’s sear – the part of the trigger mechanism that holds the hammer in place.

Baldwin’s defense contends that competing analysis “contradicts” the state’s theory that the gun was in proper working order, and that prosecutors withheld supplemental reports into the gun’s condition for nearly nine months.

They argue that prosecutors showed “flagrant disregard” in their obligation to turn over relevant evidence to the defense and had played “hide the ball” in order to “win at all costs”.

On Friday, a New Mexico judge denied an earlier request from Baldwin’s team to dismiss the charges against him, and will consider a separate motion at a hearing on Monday.