Richard Stroman was stabbed “until his blood was running down the walls and pooling around his lifeless body,” Assistant District Attorney Gretchen Lundgren told a Suffolk Superior Court jury at the close of his alleged killer’s murder trial this morning.

It was LARRY NELSON (D.O.B. 1/5/58), Lundgren said, who on Oct. 7, 2007 stabbed the 64-year-old Stroman 20 times on his face, neck, torso, arms, hands, and back in the victim’s Roxbury home before taking several items and fleeing the apartment. Nelson is charged with first-degree murder for Stroman’s homicide.

Lundgren said the stabbing was so forceful that Nelson sliced his own hand during the attack, leaving a trail of blood through the apartment, down a set of stairs, and out a rear door. Before fleeing, however, Nelson “took the time to look through the apartment for valuable items,” Lundgren told the court. “And when he left, he had [the victim’s] wallet, pill bottle, cell phone and guns.”

“What did he do next? He went to get help for himself,” Lundgren said. Nelson called a friend who had some medical training and asked her to meet him in Jamaica Plain. After she arrived, he allegedly asked her to sew up his severely wounded hand with a needle and thread. The friend refused, Lundgren said, and insisted that he go to the hospital. Lundgren told the court that instead of going to one of five nearby Boston hospitals, Nelson asked to be driven to a Cambridge hospital.

While at the hospital, Lundgren said, Nelson told a series of lies to medical professionals and Cambridge and Somerville police officers. “He told [them] that he was the victim of an attempted robbery, that he put up his hand to block a knife coming towards his throat,” Lundgren said. Nelson subsequently “changed his story five times,” she said.

“His deception knew no bounds, and he had the audacity to present himself as a victim,” the prosecutor told the court.

That deception, Lundgren said, was unraveled during the course of an extensive police investigation culminating in a March 11, 2008, interview of the defendant by Boston Police homicide detectives.

“On that date [the detectives] were armed with information regarding the activity on Mr. Stroman’s cell phone,” Lundgren said. Nelson had called Stroman on Oct. 4, 5, 6, and five times on Oct. 7, she said. After Oct. 7, “the defendant never tried to call Richard Stroman again. Why? The obvious answer: Because he knew [Stroman] was dead.”

Detectives asked Nelson to provide them with a DNA sample, which he did. The defendant’s DNA was later matched to the blood trail leading out of the victim’s apartment.

“His trail of lies couldn’t cover up his trail of blood,” Lundgren said.

“Uncontroverted DNA evidence places Larry Nelson inside of Richard Stroman’s apartment and proves that he murdered Richard Stroman,” she said. “He didn’t just murder him, he murdered him with extreme atrocity and cruelty.”

Lundgren told the jury that 11 of the 20 wounds sliced the victim’s skin and soft tissue, while the remaining wounds penetrated organs, major arteries, cartilage, muscle and bone. Stroman also sustained defensive wounds to both hands and arms.

“He was alive and could feel each and every one of those wounds,” Lundgren said. “He was in pain.”

On Oct. 12, 2007, one of Stroman’s Elm Hill Avenue neighbors contacted authorities after detecting a strong odor coming from his apartment. When Boston Police gained entry to the residence, they found the victim lying dead in his hallway in a pool of blood.

“In the end, the evidence proves that the defendant is guilty of killing Richard Stroman,” Lundgren said.

Nelson was arrested on April 4, 2008, and subsequently charged with Stroman’s murder.

After closing arguments, Judge Judith Fabricant instructed jurors on the law before releasing them to begin their deliberations. They will resume their deliberations tomorrow morning.

Jennifer Stott is the district attorney’s victim-witness advocate on the case. Nelson is represented by attorney John Palmer.