In new court documents filed Wednesday ... Morrissey went after Judge Mary Marlowe Sommer's grounds for dismissing the case -- in which she ruled Baldwin had been prejudiced by the prosecution's suppression of evidence.

This meant Baldwin could not be charged with involuntary manslaughter in the case again ... but prosecutors are now asking the judge to reconsider her ruling.

In the docs, the prosecutor insists that although certain evidence had been suppressed -- which included live rounds of ammunition found on the set -- Baldwin's defense team was aware of its existence prior to trial and, in any event, the evidence was not material to his defense in any way.

According to prosecutors, "there was no cover-up because there was nothing to cover up."

The live ammunition in question was first turned over to the Santa Fe County, New Mexico sheriff's office during "Rust" armorer Hannah Gutierrez-Reed's trial.

Reed is now serving an 18-month prison sentence after being found guilty of involuntary manslaughter ... after the film's cinematographer, Halyna Hutchins, was shot and killed by a gun held by Baldwin on set.

As for the live ammunition evidence ... it was later revealed the evidence was actually filed under a different case number -- but Baldwin's attorneys said they were not notified of this.

The prosecutor maintains "it was still Alec Baldwin's responsibility to handle his real prop gun safely and not point the gun at anyone (let alone two people at the same time), cock the gun when the scene did not call for it and pull the trigger of the gun when the scene did not call for him to pull the trigger."