Breaking news update: Alexis Simpson has been found not guilty on all charges relating to the stabbing death of her roommate Dominique Frazier. The jury deliberated Thursday for less than three hours. Stay with for more details.

From Keaira Johnson’s perspective, Alexis Simpson instigated the confrontation that left her roommate at Bowie State University fatally wounded. But Johnson, who saw the deadly fight, acknowledged in court Wednesday that Simpson might not have intended to slash her roommate’s neck.

Simpson, now 20, is on trial on charges of first-degree murder in the September 2011 slaying of 18-year-old Dominique Frazier, her roommate in the Christa McAuliffe residence hall. Prosecutors say that the women did not get along and that Simpson stabbed and slashed Frazier during a fight in their shared suite.

Defense attorneys say that Simpson was bullied by Frazier and her friends and retrieved and wielded the knife in self-defense.

Johnson, 21, a friend of Frazier’s, testified Wednesday that Simpson and Frazier began to argue after Simpson turned off an iPod playing in the suite and that Simpson soon began yelling outside the door to Frazier’s room.

Keiara Johnson witnessed the confrontation between roommates Alexis Simpson and Dominique Frazier, which ended with Frazier fatally wounded. (Sarah L. Voisin/The Washington Post)

Johnson testified that after Frazier retrieved a knife — not the weapon used in the slaying — she quickly moved to take it from her and stash it in a dresser drawer.

“I said, ‘You’re not going to do that,’ ” Johnson testified. “You’re not going to stab her.”

Soon after, Johnson testified, Simpson came into the room and began to fight Frazier, and the brawl spilled to the living room. Johnson said that after that fight paused, Simpson punched her and the two of them traded blows.

After the melee had appeared to end, Johnson testified, Simpson again went to Frazier’s room. She said that the women “started swinging at each other” and that Frazier “grabbed her neck and just stopped moving,” apparently having been slashed.

That account is in line with other witnesses’ and prosecutors’ theory of the case. But defense attorneys forced a key concession from Johnson when she acknowledged on cross-examination that Simpson might not have intended to slash Frazier.

“It looked like a mistake, right?” Christopher Griffiths, Simpson’s defense attorney, asked Johnson.

“I guess. Yeah,” Johnson said.

Defense attorneys on Wednesday began calling their own witnesses, first questioning two Bowie State juniors who said they witnessed incidents involving Simpson, Frazier and Frazier’s friends.

Elliott Styles and Unique Arnold testified that they saw some women glaring at Simpson in a cafeteria area at the university after an argument. Previous testimony indicated that those women were Frazier and her friends. Arnold said that about a week before the stabbing, Simpson told her that she intended to change dorm rooms.

Another defense witness, Janaye Ruffin, who lived across the hall from Frazier and Simpson, testified that after the slashing, Simpson seemed “scared” and “concerned.”

“She was breathing heavy,” Ruffin said. “She couldn’t even put words together to form sentences.”

Prosecutors concluded their portion of the case by calling a medical examiner, who testified that Frazier died of “multiple sharp force injuries,” including a cut to the jugular that could have proven fatal in seconds.

The trial was expected to resume Thursday.