The case seemed doomed.
After years of trying to tie a drug dealer to the murder of Rebecca Payne, a 22-year-old Northeastern University student, investigators’ most valuable witness died.
The death of Anthony White, the only person willing to place the alleged killer at the scene, forced Suffolk prosecutors to consider dropping the case.
“They said it will be a miracle to get this case back up and running again,” said Nicholas Payne, Rebecca’s father.
But last month, something approaching a miracle happened. As prosecutors were preparing to tell a judge they would not be able to try the man charged with Payne’s killing, 32-year-old Cornell Smith, new evidence surfaced from an unlikely source — the defendant’s own hand.
Smith, it turned out, had written a letter to a judge implicating himself in the killing, according to prosecutors.
“Out of anger from an altercation that had happened downtown Boston, [they] . . . set up an occurrence which was leading to the unfortunate passing of Rebecca Payne at the hands of I, Cornell Alan Smith Sr.,” he wrote.
The letter has revived hopes of a resolution in the killing of Payne, a promising senior from New Milford, Conn., who prosecutors said was killed in a case of mistaken identity.
At 3:30 a.m. on May 20, 2008, Payne was lying on her couch in her Mission Hill apartment when a gunman slipped through an unlocked balcony door and shot her four times. Neighbors heard the shots and her screams but no one called the police. The building manager found her body the next day.
The neighbors’ silence infuriated police, and the killing terrified residents of Mission Hill, a neighborhood that had just finally begun to feel safer after years of violent gang rivalries and shootings. When police arrested Smith in 2012, the Paynes said they could finally grieve for their only child.
Upon his retirement in 2013, Police Commissioner Edward F. Davis said solving the killing was one of his proudest moments in the department, along with the capture of those responsible for the Boston Marathon bombings.
Still, the case was vulnerable. Prosecutors had witnesses who would testify that Smith had an ongoing rivalry with another drug dealer, a woman with a strong resemblance to Payne who lived at the same apartment complex and who earlier that month stabbed Smith during a fight, according to court documents.
The prosecutors also had surveillance video that shows a fleeing sport utility vehicle that prosecutors say looks like a Ford Expedition belonging to a customer of Smith’s, who had agreed to drive him to Mission Hill in exchange for crack cocaine. But the customer, Michael Balba, denied he had been with Smith that night when the shooting happened.
There is no physical evidence tying Smith to Payne’s apartment, which was why the testimony of White was so crucial.
White was prepared to testify that he had been with Smith that night, that Smith had told him he planned to rob his rival, and that he heard the shots while he sat in the Ford Expedition waiting for Smith. White, a cocaine dealer, agreed to testify in exchange for leniency on his own drug charges.
The trial was delayed at least twice — in August 2012 Smith’s first lawyer withdrew from the case after Smith hit him during a hearing. Then, Smith’s second lawyer became too ill to continue with the case two months before the trial was scheduled to start in October 2013.
Veteran defense attorney John Amabile was appointed as Smith’s third lawyer, and the trial was rescheduled for December 2014.
But White, 33, died in May at St. Vincent’s Hospital in Worcester from health complications from an unrelated 2008 shooting that left him blind and in a wheelchair.
The Paynes learned about White’s death from prosecutors on May 20, the sixth anniversary of their daughter’s death. They were in Boston to place candles at a rock bearing her name at the Garden of Peace — a memorial to homicide victims across the street from the Suffolk Superior Courthouse.
“That was not a good day,” Nicholas Payne said.
The Paynes prepared themselves for the possibility that Smith, who is serving both federal and state drug sentences on unrelated charges, would be free by 2019 — and that, with White’s death, he would never be tried for the slaying of their daughter.
But on Oct. 28, the prosecutor in Smith’s Superior Court drug case, who was trying to gather more information about Smith’s federal drug case, was scrolling through documents filed in US District Court. One caught his eye — a March 4, 2014, letter written by Smith and sent to US District Court Judge William G. Young.
Six pages long, neatly written and single-spaced, the letter was incomprehensible at points. Smith described himself as the victim of rape on a crusade to stop other sexual assaults and the target of enemies that ranged from street dealers to high-level prosecutors.
But the single line on page 5 — the line in which Smith appears to identify himself as the killer — had the potential to save the case.
Prosecutors immediately told the Paynes.
“Sounds like our miracle,” Nicholas Payne thought.
Ian Polumbaum, who is the prosecutor in Payne’s case, acknowledged in court last week that the letter could be dismissed as the rantings of a troubled defendant. Amabile hinted that he might use such a defense if the letter is used as evidence against Smith. A hearing will be held on Dec. 2 to discuss the new evidence.
The Paynes said they still hope the man who allegedly provided the getaway car, Balba, who has been charged with perjury for allegedly lying to a grand jury, will bolster the credibility of the letter by testifying against Smith.
But with the myriad twists the case has taken, they temper their expectations to avoid crushing disappointment.
Said Nicholas Payne: “You know how an agonizing ache just becomes a dull ache after a long time?”
Maria Cramer can be reached at mcramer@globe.com. Follow her on Twitter @globemcramer.