PORTLAND – A teenager whose 16-year-old brother was stabbed to death in the doorway of their family’s Congress Street apartment came under sharp cross-examination by the defense at the murder trial of the man he identified as the killer.

Defendant Brandon Mills’ lawyer aggressively questioned Herman Ramirez, 15, about his own criminal record as well as about inconsistent statements he made to police and in court.

Ramirez testified that he saw Mills pull out a knife and stab Jarmaine Ramirez during the Oct. 21 confrontation that came about after Mills and his brother allegedly sought to settle a score with youngsters who were tossing water out a second-floor window and onto the street.

At one point during Tuesday’s cross-examination, defense counsel Daniel Lilley suggested that Ramirez himself may have been responsible for the killing.

“In the heat of all that was going on the day your brother died, did you mistakenly stick a knife into your brother?” Lilley asked.

“I know who killed my brother,” said Ramirez, gesturing toward Mills. “He did.”

Testimony resumed Wednesday in Cumberland County Superior Court and was expected to continue into next week.

Ramirez, a key prosecution witness, had given contradictory statements about the moments before and after his brother’s death. He also has a conviction for theft, and was charged with carrying a concealed knife shortly before the incident.

During cross-examination, Lilley confronted the witness with statements he made at Mills’ January bail hearing in which he testified that he never carried a knife.

The lawyer asked Ramirez to compare those statements with the fact that he had been charged with carrying one in Biddeford.

“You were lying, were you not?” Lilley asked.

“I wasn’t lying,” Ramirez answered. “I forgot.”

Ramirez’s mother said her son’s hearing and speech problems make him difficult to understand. Ramirez also has learning disabilities that at times made him unable to understand some of the documents he was asked to review in court, Bonnie Ramirez said.

Mills’ brother, Antwane, was also charged with murder, but pleaded guilty in February to burglary and assault. He faces three years in prison, with all but 18 months suspended.