A man convicted in a 1995 Boston homicide that triggered a bloody civil war in the city’s Cape Verdean community was granted a new trial Wednesday by the state appeals court because his family was kept out of the courtroom for part of the time when the jury was chosen.

Nardo Lopes allegedly stabbed Robert “Bobby’’ Mendes to death on a Dorchester street on Oct. 10, 1995, and then spent 12 years on the run before he was captured by authorities while returning home to Baltimore from a vacation in Jamaica in 2007.

In a unanimous ruling Wednesday, a three-judge panel of the Massachusetts Appeals Court ordered a new trial for Lopes on the grounds that his Sixth Amendment right to a public trial was violated because his family was kept out of the court for about 90 minutes while jurors were being chosen.

“While the judge proceeded in a manner that showed regard for the defendant’s rights, the record does not indicate that she explored whether reasonable alternatives to a complete closure of the court room existed once the issue was brought to her attention,’’ the court ruled. “The closure of the court room here violated the defendant’s Sixth Amendment right to a public trial. Consequently, the judgment must be vacated.’’

Charged with murder, Lopes was convicted in 2008 in Suffolk Superior Court of the lesser charge of manslaughter and sentenced to 8 to 12 years in state prison for the killing, which authorities said triggered 24 murders and numerous stabbings in the Cape Verdean community.

Mendes, 23, was the son of Isaura Mendes. She has worked since the 1990s to end street violence in Boston, especially in the Cape Verdean community. She lost a second son, Alexander, 24, to homicide in 2006. In a telephone interview, Mendes indicated she was not interested in seeing Lopes tried again.

“I am done with Nardo,’’ said Mendes, who forgave Lopes in 2008 for killing her son. “If God and the Parole Board and the court system decide to let him out, that’s all about them. It’s not about me.’’

According to the Appeals Court, about 90 potential jurors — called a venire — were brought into a Suffolk Superior courtroom, where they occupied every seat and 10 were forced to stand. Lopes’s defense attorney demanded that room should be made to allow Lopes’s family to remain.

But, according to the Appeals Court, Superior Court Judge Linda Giles ordered Lopes’s family out of the courtroom to keep the family and prospective jurors apart. She also ordered that the family be allowed to return when space opened up as people left after being rejected as jurors.

After about 90 minutes, Giles noticed that family members had been able to return to what was then a partially empty courtroom. But no effort had been made to return the family members individually as soon as seats opened up, the court found.

Rubin wrote that if the trial judge had documented that she tried to, but could not, accommodate Lopes because of security or other issues, the exclusion of family could have been justified. But Giles did not demonstrate that she had investigated alternatives, Rubin wrote.

A spokesman for Suffolk District Attorney Daniel F. Conley said prosecutors will ask the Supreme Judicial Court to overturn the lower court decision.

Lopes was paroled from state prison on Aug. 6, 2015, according to the state Department of Correction. His appellate attorney, Derege B. Demissie, said he regretted the order for a new trial came only after Lopes has served a “significant’’ amount of time behind bars.

“This is a really good example of why courts should give serious consideration for a stay [of a prison sentence] pending appeal,’’ Demissie said. The ruling “sends a clear message that court convenience never trumps a defendant’s right to a public trial.’’

John R. Ellement can be reached at ellement@globe.com. Follow him on Twitter @JREbosglobe.