For the first time, Arnaldo ``Nardo'' Lopes yesterday publicly described the fatal fight he had on a Dorchester street nearly 13 years ago, a killing Boston law enforcement officials say ignited a civil war inside the city's Cape Verdean community that has killed dozens.

Lopes admitted fatally stabbing 23-year-old Bobby Mendes on Wendover Street on Oct. 10, 1995, but calmly insisted to a Suffolk Superior Court jury that he acted in self-defense.

Lopes was 17 years old when, he said yesterday, he slammed the blade of a folding knife into the chest of the older Mendes, whom Lopes said was attacking him with a piece of metal as two of Mendes's relatives hammered him with pieces of wood.

``At that point, I reacted and ended up swinging at Bobby,'' said Lopes, who is on trial on second-degree murder charges.

Lopes, now 30 years old, had been on the run since the stabbing and was finally captured by Boston police in 2007 outside Baltimore.

Listening to Lopes as he described the confrontation was Mendes's mother, Isaura, who used her son's death to become an antiviolence advocate in the city. She lost a second son, Alex, to what police have described as gang-related violence in 2006.

``I never said my children are angels. But we are from Dorchester . . . and it is not easy for our children,'' she said in an interview after Lopes testified. ``But at the same time, no one has the right to take a life.''

Prosecution witnesses called by Suffolk Assistant District Attorney Dennis Collins described Lopes as a violent teen who falsely suspected Mendes family members of ``snitching'' on him to Boston police in a gun case.

At the time of the fight, Lopes was being prosecuted in juvenile court on gun possession charges, but a police officer testified last week Lopes was charged because he was spotted by a police officer, running with a gun in his hand.

Lopes insisted on the stand yesterday, however, that prosecution witnesses were wrong and that he did not see any connection between his arrest on the gun charges and Mendes.

Instead, he said, he was riding his bike on Wendover Street when Mendes's relative, Larry Andrade, began arguing with him, and then knocked him to the ground. Andrade has since been murdered in one of an estimated 24 killings authorities have attributed to fallout from Mendes's death.

Lopes also said that Mendes attacked him and was not the peacemaker prosecution witnesses have described.

`` `I'm going to (expletive) him up,' '' Lopes quoted Mendes as shouting after he was stabbed. Mendes then collapsed.

The jury is likely going to be allowed to consider his life on the run as the act of a guilty man, officials said. At the prompting of his Brockton-based lawyer, Kevin J. Reddington, Lopes yesterday tried to explain to the jury why he chose to avoid the trial they are now a part of.

Lopes said that he was chased from the scene, that his family's home was surrounded by Mendes's relatives, and that he told police in a 911 call he had acted in self-defense.

He said he feared he would be killed if he stayed in Boston. .

``My initial plan was to turn myself in,'' he said. ``But the time never really felt right.''

The jury is expected to begin deliberations today.

John Ellement can be reached at ellement@globe.com.