“This is a domestic violence murder – nothing more, nothing less,” a Suffolk County prosecutor told a Superior Court jury this afternoon in an opening statement of a Dorchester man’s murder trial.

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

Assistant District Attorney Ian Polumbaum told the court that on the evening of February 14 – Valentine’s Day – Gonzalez, Forty, and her mother went out to a Uphams Corner bar to celebrate the occasion.

“At least outwardly, things appeared OK,” Polumbaum said of that evening. At about 1 in the early morning hours of Feb. 15, the trio called a car service to drive them home. Forty’s mother was dropped off at her home, and the couple continued on to the Ridgewood Street apartment they shared.

At about 2 a.m., Forty called her mother to let her know she had gotten home safely, Polumbaum said, which was something she did regularly. During this conversation, Forty told her mother that she would see her again the next day.

“She never made it there,” Polumbaum said.

Polumbaum told the court that at about 3 a.m., the defendant called 911. Gonzalez told Spanish-speaking Boston Police dispatchers that someone had come into the apartment and stabbed his wife – a term he used to refer to his girlfriend, Polumbaum said.

When Boston Emergency Medical Services responded to the scene, “the defendant was there to let them in with a fresh scratch on his nose and blood on his shirt.”

Forty, who was still alive, was lying on a bed soaked with blood, Polumbaum told the court. When asked who had done this to her, Forty said, “I don’t want to die,” and begged paramedics, “Please don’t let me die.”

While EMTs attended to the victim, a Spanish-speaking Boston Police officer spoke with the defendant. Gonzalez repeated his story of an intruder, Polumbaum said, and told the officer that he had sustained the cut to his nose from a fight that had happened a few days prior.

Forty was taken in an ambulance and rushed to a local hospital. While in the ambulance, paramedics asked her if her husband had done this to her, to which she responded in the affirmative, Polumbaum said.

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

Emergency room doctors tried to save her life, Polumbaum said. Forty sustained 11 stab 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.

She died several hours after being rushed to the hospital. “Dead, the evidence will show, from first-degree murder,” Polumbaum said.

Police took Gonzalez into custody after hearing about Forty’s statement in the ambulance. In a post-Miranda statement to a Spanish-speaking Boston Police officer, “the defendant’s version of the story changed,” Polumbaum said.

Gonzalez 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. He also claimed that he apologized, helped her into bed, and called 911 immediately after the stabbing.

“Evidence will show that he did a little more than that,” Polumbaum said. “He made the effort to clean up, to cover up.”

The knife used in the attack was never positively identified, Polumbaum said, although several knives were found in odd places around the house and a knife was found outside the apartment on the sidewalk. “No blood was detected,” on any of those knives, Polumbaum said.

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 his girlfriend in the apartment. He also said, “I don’t know how many years I’m going to get, because the police got me.”

Forensic investigators were able to positively identify blood stains on the defendant’s boxer shorts and shirt as matching Forty’s DNA profile.

They also recovered a pajama top and grey fleece that Forty had been wearing on the night of the stabbing. “Each garment had 11 cuts in it,” Polumbaum said. “Eleven points of violence to Miss Forty’s body.”

Gonzalez is represented by attorney Willie Davis. Proceedings are ongoing before Judge Geraldine Hines in courtroom 808 of the Suffolk Superior Court.