BOSTON -- The retrial of a former Harvard graduate student accused of killing a Cambridge man in a street fight got under way on Wednesday.

Alexander Pring-Wilson was convicted in 2004 of manslaughter in the stabbing death of Michael Colono.

Pring-Wilson's manslaughter conviction was overturned after his attorney successfully argued that evidence of the victim's violent past should have been allowed at trial. Four years later, Pring-Wilson's defense remains the same: he acted in self-defense during the April 12, 2003, street fight with Colono and his cousin.

"Alexander Pring-Wilson had a Spyderco military folding knife in his pocket and he was ready and willing to use it," prosecutor Adrian Lynch said in her opening statement.

But Pring-Wilson's defense attorney said Colono was the aggressor that night and teamed up with his cousin to beat Pring-Wilson to the ground.

"How long was he supposed to take it and take it some more? How long was he supposed to do nothing but hope they stopped on their own before the next blow killed him or turned his brains to mush?" asked defense attorney Peter Parker.

Colono's cousin testified during the first trial that Pring-Wilson stabbed Colono repeatedly after Colono made fun of him.

Parker said Colono had violent past, including a fit of rage at a local pizza shop.

"And you are going to hear that Colono threw his money into the cashier's face, went into a rage, and on the way out, kicked and smashed a plate-glass door, shattering it," Parker said.

On Wednesday morning, the jury toured the spot on Western Avenue in Cambridge where the fight took place.

"The events that happened that are at the heart of this case happened at close to 2 in the morning on a dark and rainy night. So it is going to be hard for us to imagine because we are going in bright daylight what that was like," Parker said.

"Being able to go and view (the scene) will just assist you when you are looking at the pictures to acclimate what exactly you are looking at in relation to other items," Lynch said.

"If the commonwealth fails to prove beyond a reasonable doubt that the defendant did not act in self-defense, then you must find the defendant not guilty," Judge Christopher Muse told the jury.