The Supreme Judicial Court on Monday ordered a new trial for David Nicanor Diaz Perez of Mattapan, sentenced to life without parole on charges he shot a man in the back outside a baby shower at the Roslindale Amvets post in 2003.

The state's highest court agreed with a Suffolk Superior Court judge that Diaz Perez was deprived of a fair trial, his second in the case, because his lawyer had failed to call an alibi witness from his first trial, which ended with a hung jury.

At that second trial, in 2007, Diaz Perez was convicted on a charge of first-degree murder for the death of Quirico Romero Jr., 19, on March 23, 2003, around midnight, outside a baby shower at Amvets Post 1, 119 Belgrade Ave.:

"The baby shower was attended by roughly one hundred guests (including the defendant), many of whom did not know one another. The event was held inside a hall, and featured both a disc jockey and an open bar. As midnight approached and the event concluded, the guests began to gather outside. An argument then broke out between the shooter, his companion, and another guest in the street outside the hall. This argument escalated into physical violence. Eventually, the shooter produced a gun, firing it once into the air and then twice more. The victim, who also had been outside but who had not been involved in the initial confrontation, attempted to flee after the first shot was fired. He was shot in the back and later died of his injuries."

The court then outlined Diaz Perez's trials, both of which focused on eyewitness accounts, because while police recovered a gun about two months after the murder from which the fatal bullet came, prosecutors were unable to tie it to Diaz Perez.

"While investigating the shooting, the police prepared a photographic array containing the defendant's photograph. This array was shown to six individuals who claimed to have witnessed the shooting or the preceding altercation. Only two of them identified the defendant as the shooter. Neither witness had seen the defendant before the baby shower, and only one of them claimed to have seen the defendant actually fire the gun. Both witnesses identified the defendant as the shooter at trial and were cross-examined. The Commonwealth also introduced corroborating eyewitness testimony regarding the shooter's appearance, including his ethnicity, height, and attire."

In the first trial, Diaz Perez's lawyer called a witness who said he was inside the hall during the shooting - and that so was Diaz Perez. In his second trial, though, Diaz Perez's new lawyer did not call the man. In its summary of the trial, the court said that while she learned of the alibi witness late, she still had enough time to put him on the stand - and was unable to explain why she did not.

In an appeal hearing in 2018, the judge in his second trial, Janet Sanders, concluded that the lawyer had provided "ineffective assistance of counsel," which was a serious enough issue to warrant a new trial altogether.

"The judge described the Commonwealth's case as "far from overwhelming," noting that only two out of six eyewitnesses presented with the photographic array had identified the defendant as the perpetrator. She also observed that the incident took place at night following a party where alcohol had been consumed. Accordingly, she wrote that evidence "placing the defendant elsewhere when the shooting occurred would necessarily be important." The judge was not persuaded that issues with Sanchez's testimony, including inconsistencies between his account of events and those given by other witnesses, would have negated the impact of the testimony; such issues were for the jury to decide. In September of 2018, the judge therefore allowed the defendant's motion for a new trial."

The Suffolk County DA's office appealed that ruling, arguing that Diaz Perez's second lawyer did just fine, he got a fair trial and he deserves to spend the rest of his life in prison without a chance at parole. But in its own ruling today, the SJC said it agreed with Sanders that the omission of the alibi witness deprived Diaz Perez of his Sixth Amendment right to a fair trial, and ordered a new trial.

The court said that Diaz Perez's lawyer in his second trial failed to adequately investigate why the first trial might have ended with a mistrial; that had she done so, she might have devoted more attention to the issue of the role of the alibi witness in leading to that result. And when she finally learned of the witness's importance and asked for a delay in the trial, she should have told the judge why she was seeking a delay, but didn't.

The court took the lawyer to task for that:

"Absent a reasonable investigation, defense counsel lacks sufficient information to evaluate his or her strategic options and to make decisions in the best interests of the client.

"The requirement of a reasonable investigation includes a duty to pursue witnesses with potentially exculpatory testimony. Here, the judge found that, although successor counsel was aware of Sanchez [the alibi witness] and that he had testified at the first trial, she made no attempt to locate or to speak with him, either personally or through a private investigator, nor did she discuss his testimony with the defendant's previous counsel. As a result, successor counsel lacked the ability to determine whether calling Sanchez as a witness might have bolstered the defendant's case, or weakened that of the prosecution. As the judge reasoned, 'With no knowledge about [Sanchez's] prior testimony, [successor counsel] was not making a strategic decision; that would have required some knowledge of what Sanchez had to say.' "

The court continued:

"Because the motion judge found 'no credible explanation for not calling [the witness],' we affirmed the judge's conclusion that counsel had been ineffective. ...

"Similarly, Sanchez provided testimony contradicting the Commonwealth's theory of the case at the defendant's first trial, and a mistrial was declared. So, at least some credible explanation from successor counsel was required as to why Sanchez was not called at the second trial."

But did this omission make a difference at the second trial? The court concluded it did: Since the case relied almost entirely on testimony from eyewitnesses, in an era when evidence shows eyewitness testimony is not always accurate, the omission of a witness who might have placed Diaz Perez away from the scene - even if, at the first trial, prosecutors had poked holes in his testimony - helped to seal his fate during jury deliberations.

And so, the court concluded, Sanders did not abuse her power in ordering a new trial:

"Here, cognizant of all that had happened at trial, the judge determined that Sanchez's testimony 'necessarily [would] be important' to the jury's deliberations. This statement functions as an implicit finding that a reasonable jury could have credited the testimony. The judge therefore did not abuse her discretion in deciding that, rather than substituting her own judgment, it should be left to the jury to assess the value of Sanchez's testimony."