A judge in New Mexico declined on Monday to grant a new trial to the armorer in the fatal “Rust” shooting, who had accused the prosecution of suppressing evidence.

The armorer, Hannah Gutierrez-Reed, is serving an 18-month prison sentence and had asked to be retried on an involuntary manslaughter charge in New Mexico after the same judge dismissed the case against Alec Baldwin during his trial in July. Judge Mary Marlowe Sommer found then that the state had withheld evidence that could have shed light on how live rounds got onto the film set.

On the afternoon of Oct. 21, 2021, Mr. Baldwin was positioning the old-fashioned revolver for a tight camera framing when the weapon discharged, killing the movie’s cinematographer, Halyna Hutchins, and wounding its director. A jury convicted Ms. Gutierrez-Reed, who loaded the gun that day, of manslaughter in March after prosecutors argued that she was reckless in overseeing guns and ammunitions on the set.

Judge Marlowe Sommer ruled on Monday that the suppressed evidence that felled the Baldwin case — a set of ammunition that was delivered to law enforcement on the day of the armorer’s conviction — did not warrant dismissal of Ms. Gutierrez-Reed’s trial because her lawyer was aware of and had access to the evidence.

The judge wrote that the ammunition “does not qualify, as a matter of law, as material evidence because it was available to defendant in advance of and during trial.”

The ruling was a moment of relief for the prosecution after its case against Mr. Baldwin, 66, collapsed under an accusation that state investigators had intentionally withheld the ammunition from them by putting it under a new case number. The accusation led to an extraordinary hearing in which the judge examined the ammunition in the courtroom; the lead special prosecutor, Kari T. Morrissey, called herself as a witness; and the other prosecutor on her team resigned.

The New York Times