As a Dorchester man’s trial for allegedly murdering his girlfriend came to a close this morning, a Suffolk County prosecutor displayed a picture of her fatal injuries on a viewing screen for the jurors who will weigh the case.

“How was that possibly self defense? How was that possibly mitigated? How was that possibly reasonably provoked? How was that possibly mutual combat? Don’t confuse retaliation with self-defense,” Assistant District Attorney Ian Polumbaum said.

MARIO GONZALEZ (D.O.B. 7/28/79) is charged with first-degree murder for fatally stabbing his girlfriend, 38-year-old Luz Forty, in the early morning hours of Feb. 15, 2009.

Polumbaum apologized to jurors for having to show them the graphic photograph of Forty’s body but said, “You need to look at it because Luz Forty’s body was murdered.”

During four days of trial, Polumbaum introduced evidence and testimony suggesting that Gonzalez, Forty, and her mother went to a Dorchester bar in celebration of Valentine’s Day 2009. At about 1:00 a.m., the trio called a car service to drive them home, first dropping off the victim’s mother, then the couple, who shared a Ridgewood Street apartment.

When Forty got home, she called her mother, as she often did, to let her know she had arrived safely. It was shortly after this phone call, prosecutors say, that the violence began.

Forty sustained up to 11 separate stab wounds to her body, including wounds to her back, left chest, shoulder, and hands. Some of the stab wounds were four inches deep, Polumbaum said, and pierced her lungs and spleen.

“Why did this happen?” Polumbaum told the court. “You will never know exactly why. You don’t need to know why. It’s a domestic violence murder, and a defendant who visited extreme violence towards a woman.”

The defendant himself called 911 following the stabbing, while the victim lay in a bed bleeding and struggling to breathe, but still alive.

“While she’s bleeding in that apartment, he’s making up a story, blaming it on someone else,” Polumbaum said.

Gonzalez allegedly told a police dispatcher that he had been out drinking, and that he found Forty stabbed and bleeding in the apartment when he got home, Polumbaum said.

When emergency medical technicians and Boston Police officers arrived on the scene, they found Gonzalez in the apartment with a cut on his nose and a swollen lip, and Forty in the bedroom, dying.

“I don’t want to die,” she purportedly said. “Please don’t let me die.”

While first responders attempted to save her life, Polumbaum said, Gonzalez did not show any sign of emotion or concern for her condition. When EMTs rushed her into an ambulance, he did not ask which hospital they were taking her to.

“He didn’t care,” Polumbaum said. “He was thinking about himself.”

While in the ambulance, one of the paramedics treating her asked whether it was her “husband” who had done this to her – the term she used to refer to Gonzalez. She responded in the affirmative, Polumbaum said.

When asked again who did this to her, Forty said “husband” in English.

The paramedic relayed this information to a Boston Police officer on the scene, and Gonzalez was taken into custody. In a post-Miranda statement to a Spanish-speaking Boston Police officer, Gonzalez told a different story of what had happened. He claimed that Forty had hit him with a bottle first, and had attacked him with a knife, which he then twisted around and used to stab her multiple times, Polumbaum said. Gonzalez also claimed that he apologized, helped her into bed, and called 911 immediately after the stabbing.

Gonzalez also made a recorded phone call to a friend from the C-11 booking desk. In that phone call, Polumbaum said, Gonzalez indicated that he had stabbed Forty in the apartment.

Despite the extensive efforts of emergency room doctors to save her life, Forty died within hours due to the numerous injuries she sustained in the stabbing.

“She didn’t die quickly,” Polumbaum said. “She did suffer.”

Calling the defendant’s stories of what transpired that night “ridiculous lies,” Polumbaum said, “This is as bad as it gets. This is a domestic violence first-degree murder, and ultimately nobody can shy away from that …. He had options and he chose the path of extreme violence.”

Gonzalez allegedly mopped the floors and either discarded or cleaned the knife that was used during the attack; that knife was never positively identified. Forensic investigators were able to positively identify blood stains on the defendant’s boxer shorts and shirt as matching Forty’s DNA profile.

“Luz Forty was 38 years old and she had a life that ended violently at Mario Gonzalez’s hands,” Polumbaum told the jury. “The proof that he murdered her will very shortly be in your hands.”

Katherine Moran is the victim-witness advocate assigned to the case. Gonzalez is represented by attorney Willie Davis. Judge Geraldine Hines is presiding in courtroom 808 of the Suffolk Superior Court.