Dominique Frazier was fatally stabbed after a confrontation at Bowie State University in September 2011. (Sarah L. Voisin/The Washington Post)

By all accounts, the suitemates at Bowie State University’s Christa McAuliffe residence hall did not get along. Dominique Frazier and Alexis Simpson argued over hair in the shower and traded insults about sexuality and brand-name clothing.

That much, prosecutors and defense attorneys agree on. Who is to blame for a September 2011 confrontation that left Frazier, 18, fatally stabbed remains an open question.

Prosecutors say Simpson, now 20, stabbed her roommate after Frazier had ostensibly retreated from a fight. Defense attorneys say Simpson acted in self-defense as she tried to leave the suite where she was the target of bullying and harassment.

Jurors in Prince George’s County Circuit Court will decide later this week which version they believe — and whether Simpson is guilty of first-degree murder. On Tuesday, prosecutors and defense attorneys offered starkly different accounts of the deadly confrontation.

Assistant State’s Attorney Christine Murphy told jurors that it began when Simpson turned off an iPod playing in the suite as a group of friends drank and prepared to go to a homecoming week comedy show. The two women exchanged words, Murphy said, and Frazier and some friends retreated to Fraz­ier’s bedroom.

Murphy said that Simpson then went to Frazier’s room and began pounding on the door. A fight soon spilled from the bedroom to the living room, as Simpson punched Frazier and another young woman who tried to intervene, Murphy said.

Then — after the feuding had temporarily ceased — Simpson went to Frazier’s door, this time plunging a weapon into Frazier’s arm and slashing her neck, Murphy said.

“When faced with multiple options, look at what choices the defendant made,” Murphy said.

Christopher Griffiths, Simpson’s defense attorney, argued that Frazier and her friends had long bullied Simpson, who transferred to Bowie State from Clark Atlanta University because she could no longer afford the out-of-state school.

He said that on the night of the confrontation, Simpson “acted in self-defense,” grabbing a knife as she tried to leave the suite. Fraz­ier and two others had beaten Simpson earlier, Griffiths said, and were attacking her again when she swung the knife with her head down.

“She acted in self-defense — and she had no choice, no choice, that night,” Griffiths said.

Simpson fled after the stabbing, prosecutors said.

Frazier, a graduate of the D.C. public charter school Friendship Collegiate Academy, was studying business administration, said friends, family members and school officials. She was interested in fashion and dreamed of one day opening a restaurant, friends and family members have said.

On Tuesday, jurors heard testimony from Frazier’s mother — who told them her daughter was only a few days shy of her 19th birthday when she was killed — and from friends of Frazier who were in the suite during the incident.

Tyerell Warren tearfully told jurors how he held a towel to Frazier’s bloodied neck, begging her to stay alive.

“I’m like, ‘Just keep holding my hand. I know you’re still there,’ ” Warren testified.

Warren said that Simpson twice accosted Frazier in Frazier’s room. The first time, he said, Frazier slammed the door in Simpson’s face.

He said that at various points — including after the stabbing — Simpson claimed to have been “jumped.” She also touched the wounded Frazier, saying, “No, no, no, I didn’t mean it,” he said.

Warren said that as he held the bloodied towel to Frazier’s neck, he told Simpson, “Nobody jumped you.”

Nielah Tucker, 20, a nursing student at the University of the District of Columbia, testified that Simpson twice came banging on Frazier’s door — although she acknowledged that Frazier at one point grabbed and put away a knife herself. Simpson would not have seen that, as it happened inside Frazier’s room when Simpson was outside, Tucker said.

Warren testified he did not hear or see Simpson banging on the door immediately before the stabbing, although he said she threw the first punch.

After the first encounter, but before the stabbing, Simpson said, “This ain’t over,” according to Warren.

Simpson had asked a property manager if she could change rooms or simply move out about a week before the stabbing, Griffiths said. But the manager declined to let her change rooms and said she would forfeit her $600 security deposit should she move out.

After that, Griffiths said, Simpson began staying at her boyfriend’s and mother’s homes in the area, although she returned to the Bowie State suite to celebrate homecoming week.