The defense attorney for Alexander Pring-Wilson, the former Harvard graduate student charged with first-degree murder, attempted to undermine the credibility of a key prosecution witness yesterday, forcing him to revise parts of his testimony from an April pre-trial hearing.

Pring-Wilson faces life in prison for allegedly stabbing Cambridge teen Michael D. Colono during an altercation outside a Western Avenue pizzeria last year.

Colono’s cousin, Samuel E. Rodriguez, took the witness stand yesterday on the emotionally charged second day of Pring-Wilson’s trial.

Rodriguez, an eyewitness to the stabbing and a participant in the fight, testified to seeing Pring-Wilson holding the alleged murder weapon.

Boston attorney E. Peter Parker, who was hired to represent Pring-Wilson after the defendant’s parents reportedly fired his two previous lawyers, attacked Rodriguez’s credibility in a grueling cross-examination yesterday afternoon in Cambridge’s Middlesex Superior Court.

The Pring-Wilson legal team seeks to show that Rodriguez and Colono posed a clear threat to their client, causing him to act in self-defense.

In the April pre-trial hearing, Rodriguez said Pring-Wilson pushed Colono into a “fence.” Yesterday, Rodriguez revised that account, saying that Colono had his back to a “brick wall.”

“A brick wall in your mind is not the same thing as a fence, is it?” Parker asked.

“That is correct. It is not,” Rodriguez said, admitting that his earlier account had been inaccurate.

Rodriguez also said he himself punched Pring-Wilson outside the pizzeria moments before the stabbing. Rodriguez said he hit Pring-Wilson “square on the side of his head” but that the blow had “no effect” on the defendant.

Rodriguez said he later “was able to drop Alex to the ground.” He said Colono—who was wearing construction boots—tried to kick the defendant, but the kick didn’t connect.

Parker, questioning the witness’ account, noted that the muscular Rodriguez, who works as a bouncer, lifted weights regularly until a few months before the fight.

Parker’s cross-examination attempted to portray Rodriguez as combative.

“To you, the fight’s not over until you put a guy on the ground or he’s not getting up,” Parker said to Rodriguez. “Is that correct?”

“Either that or he admits defeat,” Rodriguez said.

Rodriguez conceded that Colono was “hot-headed” and “impulsive.” The witness also confirmed that Colono had called Pring-Wilson a “motherfucker” before the fight.

Parker contended that Rodriguez and the wounded Colono fled the crime scene by car after Pring-Wilson called 911 on his cell phone.

“That’s why y’all got in the car,” Parker said. “You didn’t want to be there when the police arrived, right?”

“That is correct,” Rodriguez replied.

Rodriguez said he gave directions from the front passenger seat while his girlfriend, Giselle Abreu, drove the car.

He admitted that his “first priority was to get out of Cambridge as soon as possible.” Even after he learned that Colono had been stabbed, Rodriguez did not tell Abreu to bring the victim to nearby Mt. Auburn Hospital.

Rodriguez, a longtime Cambridge resident before moving to Lynn, Mass., was born at Mt. Auburn and said he knew the hospital was “one or two minutes away” from the Trader Joe’s lot where Abreu parked.

It wasn’t until Abreu drove into Boston that Rodriguez sought help in front of a 7-Eleven.

Outside the convenience store, Rodriguez sought to revive Colono while bystanders called for an ambulance.

“I even smacked him once,” Rodriguez said.

“I kept asking him to stay with me, to breathe,” Rodriguez said. “I kept telling him that it wasn’t his time.”

COURTROOM DRAMA

Rodriguez’s eyes welled with tears as he recounted the final moments of his cousin’s life.

The witness stared directly at Pring-Wilson during the most emotional portions of his testimony.

Rodriguez, prompted by friendly questioning from Assistant District Attorney Adrienne C. Lynch, spoke about the tense dynamic between him and Abreu on the night of the stabbing.

Earlier in the evening, Rodriguez became embroiled in a shouting match with Abreu after she used Rodriguez’s mother’s car without permission.

The verbal dispute was so heated that neighbors in Lynn, Mass., called the police.

But Rodriguez vehemently denied that he physically assaulted Abreu.

He said he began drinking whiskey after the spat with Abreu, adding that he was “feeling mellow” by the time of the row with Pring-Wilson.

While he said he also brought a six-pack of Rolling Rock for Colono, Rodriguez said that Colono had only “cracked a beer” prior to the fight.

SETBACK FOR D.A.

Cambridge criminal defense lawyer Kevin J. Mahoney, who is not affiliated with the case, said yesterday’s testimony revealed the uncertainty surrounding the confrontation of the two parties prior to the stabbing, a potential weaknesses in the prosecution’s case.

“The idea that Pring-Wilson went over to the car to pick a fight with these guys is not borne out by the evidence,” said Mahoney, a former Middlesex County prosecutor.

Mahoney said the prosecution’s charge of first-degree murder, and not just manslaughter, was intended to extract a plea bargain.

“In Middlesex County, the usual practice is to charge everyone with first-degree murder—even if it’s manslaughter,” Mahoney said. “They’re trying to intimidate you to accept manslaughter. Pring-Wilson hasn’t been intimidated.”

—Hana R. Alberts contributed to the reporting of this story.

—Staff writer Daniel J. Hemel can be reached at hemel@fas.harvard.edu.