Prosecutors will convene a grand jury to consider whether to refile an involuntary manslaughter charge against Alec Baldwin in the fatal shooting of a cinematographer who was killed on the set of the film “Rust” in 2021, New Mexico prosecutors said on Tuesday.

“We believe that based on our lengthy and detailed investigation that it is appropriate for a grand jury in New Mexico to make a decision on whether the case should proceed,” one of the prosecutors, Kari T. Morrissey, said in an interview on Tuesday.

Mr. Baldwin was rehearsing on a New Mexico film set with a gun that was not supposed to contain live ammunition when it suddenly fired a live round, killing the film’s cinematographer, Halyna Hutchins.

In a statement on Tuesday, two of Mr. Baldwin’s lawyers, Luke Nikas and Alex Spiro, said: “It is unfortunate that a terrible tragedy has been turned into this misguided prosecution. We will answer any charges in court.”

The decision to convene a grand jury was another reversal of fortune for Mr. Baldwin, who had an earlier manslaughter charge dropped after prosecutors received new evidence suggesting that the gun might have been modified in a way that made it easier to inadvertently fire. Prosecutors decided to reopen the case after submitting the gun for further analysis, which they said contradicted Mr. Baldwin’s assertion that he had not pulled the trigger.

“The forensic testing of the gun concluded with certainty that the trigger of the gun had to have been pulled for the gun to go off,” Ms. Morrissey said in the interview. She said the prosecutors intend to begin presenting the case to a grand jury on Nov. 16. The decision to convene the grand jury was first reported by NBC News.

The decision was a stunning development in the prosecution of Mr. Baldwin, who, just six months ago, had a weight lifted from his life and acting career when the original involuntary manslaughter charge was dismissed.

The day of the shooting, on Oct. 21, 2021, the crew was setting up a tight frame of Mr. Baldwin drawing an old-fashioned revolver. Investigators said he was told the gun was “cold,” meaning in this case that it was supposed to be loaded with dummies, or inert cartridges used to resemble real bullets on camera. But when the gun went off it fired a live round, which killed Ms. Hutchins, and wounded the film’s director, Joel Souza.

A team of special prosecutors, Ms. Morrissey and Jason J. Lewis, has pressed forward on the original case filed against the movie’s armorer, Hannah Gutierrez-Reed, who was in charge of weapons, ammunition and gun safety on the set. She was also charged with involuntary manslaughter, and has pleaded not guilty.

Mr. Baldwin has maintained that he did not pull the trigger. Instead, he told investigators, he pulled back the hammer on the gun — and when he let go, the gun went off.

But the forensic gun expert the prosecutors hired to conduct a more detailed analysis found that the actor would have had to put pressure on the trigger for the gun to have gone off, providing the basis for Tuesday’s announcement.

The report by the forensic analyst, Lucien C. Haag, did not directly address whether the gun, a Pietta replica of a 1873 revolver, had been modified. But it said that it required about two pounds of pressure on the trigger to discharge — a small amount when compared to typical modern weapons but not unusual for a single-action revolver of that kind, experts said.

“Although Alec Baldwin repeatedly denies pulling the trigger, given the tests, findings and observations reported here, the trigger had to be pulled or depressed sufficiently to release the fully cocked or retracted hammer of the evidence revolver,” Mr. Haag wrote in the report, which was released through a public records request. He also included photos of Mr. Baldwin handling a revolver on set earlier in filming, highlighting the actor’s finger on or near the trigger as he was cocking the gun.

Before Mr. Haag tested the gun, it had been examined by the F.B.I., which broke parts of it during testing, a complication that is certain to be raised by Mr. Baldwin’s defense. In order to test the gun, Mr. Haag replaced the damaged parts with new ones from the same type of gun.

In making their case before the grand jury, the prosecutors will have to contend with the fact that there was not supposed to be any live ammunition on the film set, and that both the film’s armorer and first assistant director had checked the gun before handing it to Mr. Baldwin. Ms. Morrissey said that her team believes a grand jury should make the decision “about the level of culpability of the person holding the gun in their hand.”

Mr. Baldwin was initially charged with involuntary manslaughter in January, but the prosecution fell apart amid legal challenges from his lawyers.

First, lawyers for Mr. Baldwin argued that the original prosecution team — led by Mary Carmack-Altwies, the district attorney in Santa Fe County — had incorrectly charged the actor under a version of a state firearm law that was passed months after the fatal shooting in October 2021, leading the prosecutors to downgrade the charges.

Then, the actor’s lawyers asserted that a special prosecutor appointed to the case, Andrea Reeb, was violating the State Constitution by simultaneously serving in another branch of government as a state lawmaker, prompting her to step down from the case.

When the judge overseeing the case ruled that Ms. Carmack-Altwies could not appoint a new special prosecutor if she wanted to remain in charge of the prosecution, she stepped down as well, tapping Ms. Morrissey and Mr. Lewis to take over.

They have deepened the investigation into the source of five live rounds found on the movie set and have added a new charge of evidence tampering against Ms. Gutierrez-Reed, accusing her of passing off a baggie of cocaine to someone after her police interview on the day of the shooting. Ms. Gutierrez-Reed has pleaded not guilty to both charges and is scheduled to stand trial in February.

Dave Halls, the first assistant director who was in charge of safety on the set, took a plea deal after he was charged with negligent handling of a weapon, avoiding prison time.

Because of pandemic-related limitations, the original criminal case against Mr. Baldwin was not brought through a grand jury indictment but through a charge brought by prosecutors subject to the approval of a judge in a preliminary hearing.

After the initial charges against Mr. Baldwin were dropped in April, the actor quickly began to be publicly attached to new projects — something that his lawyers argued had been seriously hindered after “Rust” by the legal uncertainty surrounding him. He was announced as having filmed a comedy alongside Nick Cannon and Mickey Rourke, as well as a film about the 1970 Kent State shooting.

Mr. Baldwin’s lawyers have also been defending him against several lawsuits from crew members on “Rust.” The actor has filed his own lawsuit against Ms. Gutierrez-Reed, Mr. Halls and other crew members, arguing that their negligence caused the death of Ms. Hutchins, as well as his own suffering since the tragedy.

“Someone put a live bullet in a gun, a bullet that wasn’t even supposed to be on the property,” Mr. Baldwin said in a television interview just over a month after the tragedy. “Someone is ​responsible for what happened, and I can’t say who that is, but I know it’s not me.”