Marcus Hurd, paralyzed after he was shot in the back of the head, told a jury last March that the two men who shot him and four other people on Woolson Street wore masks or tightly pulled hooded shirts.

Edward Washington and Dwayne Moore were charged with the killings. Washington was acquitted, but the jury deadlocked on Moore. He faces a new trial next month.

Now, Hurd is saying that it was during that first trial that he recognized Moore as one of the shooters, according to documents filed recently in Suffolk Superior Court.

The development would appear to be a significant advantage for prosecutors, whose case relies heavily on another eyewitness, an admitted drug dealer, with questionable credibility. But according to legal specialists and psychologists, allowing Hurd to testify to such a different account is risky. On Tuesday, a judge will weigh whether to allow Hurd’s new recollection at Moore’s retrial in October.

Hurd, a 31-year-old handyman at the time of the shootings, had initially testified that he caught fleeting glimpses of the man who shot him, a “taller gunman” in a hooded shirt and Adidas sneakers carrying a weapon that looked like a ­machine gun.

“I couldn’t see none of their face, no skin,” Hurd said during his testimony. He did not identify either defendant from the stand.

But seeing Moore in court, prosecutors said in documents filed Friday, “caused him to recognize the shooter’s facial features (specifically his bone structure.)”

“He saw the defendant during a period of great import and highly notable events from close range and recognized him when he saw him in person for the first time since the shooting,” Assistant District Attorney Edmond Zabin wrote.

Zabin will argue Tuesday that Hurd’s new testimony should be allowed at Moore’s trial. But according to some ­legal specialists, Hurd’s testimony could end up helping Moore’s case. At issue is not just that Hurd changed his story, but also that the new assertion comes two years ­after the shooting.

“If a witness testifies that the person may have been wearing a mask and testifies in a way that is totally contradictory to their past testimony, [a defense attorney] is going to pick that apart,” said Michael Doolin, a Dorchester defense attorney and former Suffolk prosecutor. “Any time a witness gives a contrary statement . . . it usually is good for the defense. It makes the witness look like they’re not being completely candid.”

The most accurate memories are typically the ones that follow soon after a crime, said Elizabeth Loftus, a psychology professor at the University of California, Irvine, who has testified in criminal cases about witness memory.

“Many people in general and jurors in particular believe that memory for a traumatic event works something like a memory recorder,” she said. But over time, memory “becomes more and more vulnerable to other influences, more and more vulnerable to distortion.”

Last July, the New Jersey ­Supreme Court issued new instruc­tions for jurors, telling them to scrutinize eyewitness testimony carefully and remind­ing them that “human memory is not foolproof.”

Jeannine Turgeon, a trial court judge in Dauphin County, Pa., is working with Loftus and a jury instructions expert to create similar instructions for her state.

“The scientific evidence from all of the studies done is that just because a witness is certain, that does not mean that the witness’s memory is accurate,” Turgeon said. “Jurors need to know that.”

Since 1989, eyewitness identifications have resulted in nearly 75 percent of convictions that were later overturned through DNA testing, according to the Innocence Project in New York.

Still, Hurd’s new claim is ­also potentially problematic for the defense, said Robert M. Griffin, a Walpole criminal ­defense lawyer and a former Suffolk prosecutor.

The key witness against Moore is Kimani Washington, a confessed pimp and convicted drug dealer who said he took part in the home invasion and robbery that preceded the shooting, but left before the killings of Simba Martin, 21; his girlfriend, Eyanna Flonory; her 2-year-old son, Amanihotep Smith; and Levaughn Washum-Garrison, Martin’s friend who slept on a couch that night.