The New Mexico prosecutors pursuing the case against actor and producer Alec Baldwin have elected to drop the “firearm enhancement” previously included among the charges. Prosecutors originally tacked a gun enhancement on top of the involuntary manslaughter charges brought against Baldwin following the fatal shooting of cinematographer Halyna Hutchins on the set of the movie Rust.

Baldwin’s charges stem from an October 2021 fatal shooting that occurred in the midst of filming an upcoming movie. Prosecutors allege the actor fired a live round during a take, with a gun aimed squarely at the cinematographer manning the camera. The cinematographer was killed, and the film’s director was wounded in the incident.

The actor claims that he was told the gun was a “cold” prop gun, meaning it shouldn’t have had any live ammunition. He’s also claimed that he never pulled the trigger. Prosecutors allege that Baldwin failed to attend firearms training, failed to check that the gun and ammunition were not live, and that the set was riddled with safety violations and cut corners. As a producer, Baldwin was responsible for set safety. Prosecutors also argue that he should not have pointed the gun directly at anyone, regardless of the circumstances. The film’s armorer, who would have been responsible for firearm safety, training, and maintenance on set, was also charged with involuntary manslaughter.

Prosecutors charged Baldwin with two counts of involuntary manslaughter. The prosecutors included a “firearm enhancement” connected to one of the counts, which adds a five-year mandatory minimum prison sentence. A gun enhancement is not exactly a separate charge but rather is a way to seek a more severe punishment for the same charge.

When the government alleges that a defendant used a firearm in the commission of a given crime, they can ask for additional years in prison that a conviction for the “base” crime would not normally carry. Sometimes the enhancement gives prosecutors a higher upper limit for the punishment, while in other cases the enhancement raises the mandatory minimum punishment. Similar sentence enhancements can apply when a crime is connected to gang membership or when the defendant’s actions are labeled a hate crime.

The trouble with the gun enhancement used following the Rust shooting is that the prosecutors relied on laws that were not actually in effect in October 2021. The relevant gun enhancement was added to New Mexico law after the fatal incident.

The U.S. Constitution explicitly prohibits state and federal governments from adding a new crime and then punishing someone for what they did before their conduct was criminal. This is known as the “ex post facto” limitation. In a free society, people cannot walk around in fear that what they do today can be retroactively criminalized tomorrow on the whims of the government.

It’s a bit more complicated in this instance because the crime--involuntary manslaughter--certainly existed at the time of the shooting. The prosecutors were instead trying to use a sentence enhancement retroactively, which is not explicitly prohibited in the Constitution. The Supreme Court has issued a number of rulings over the years interpreting the ex post facto limitations. The Court has ruled, for example, that retroactive changes to trial procedures that do not disadvantage defendants do not trigger ex post facto concerns.

The Court has been very clear, however, that a statute that retroactively increases the severity of a criminal sentence could constitute an ex post facto violation. If a law increases the sentencing range of a criminal offense, the increased range cannot be applied retroactively to acts committed before the law was effective. The Court has even held that expanded sentence ranges that were merely advisory, as opposed to mandatory, can violate the ex post facto prohibition.

A spokesperson for the Santa Fe district attorney’s office said they chose to drop the gun enhancements against Baldwin and the Rust armorer "in order to avoid further litigious distractions by Mr. Baldwin and his attorneys." Given Supreme Court precedent on the matter, the prosecutors would likely have faced an uphill battle in court had they chosen to continue pursuing the enhancements.

Baldwin still faces up to 18 months in prison should he be convicted.