A 23-year-old Maryland woman pleaded guilty and agreed to testify against her twin sister Friday in connection with the deadly attack on their younger brother in the family’s townhouse basement.

The move by Lemae Matthews represents a major development in the long-running and bizarre case in Montgomery County, which has now implicated four people: the twins, the boyfriend of one of them and his friend. The victim, Christian Matthews, was beaten and strangled after being roused from his sleep on March 21, 2017. He was 17.

In court Friday, prosecutors read a statement from Lemae Matthews recounting how she was on the main floor during the killing.

“I heard what sounded like furniture being slammed around and Christian yelling, ‘Stop! Stop!’ ” Matthews said, according to the statement.

She pleaded guilty to accessory after the fact to first-degree murder and faces up to 10 years in prison.

She agreed to testify, according to prosecutors, if called in the pending first-degree-murder trials of her twin sister, Leaundra Matthews, and one of the men who allegedly attacked Christian in the basement, Daniel Howard, who is now 25. The second accused assailant in the basement, Tysean Lipford, was convicted of second-degree murder in 2019 and is serving a 30-year sentence.

In her statement to prosecutors, Lemae Matthews said that around the time of the killing there was bad blood between her twin sister and younger brother over Lipford, who was the father of Leaundra Matthews’s baby. When Lipford was interrogated by detectives in 2017, he confessed to killing Christian Matthews, according to court records. He said that Christian Matthews had threatened to harm Leaundra and their baby, records show.

As the twins, Lipford and Howard were discussing Christian, Leaundra Matthews allegedly said she wanted her brother gone.

“By gone, she meant that she wanted him killed,” Lemae recalled in her statement to prosecutors. “I asked her if they could just beat Christian up instead, but Leaundra said she wanted him ‘gone.’ ”

Brian Shefferman, an attorney for Leaundra Matthews, declined to comment.

“Mr. Howard pleads not guilty to these charges,” his attorney, Aaron Meyers, said Friday. “He is eager for his opportunity in a court of law to examine the state’s evidence, the state’s theories of this crime, and the many different versions of this story as told by the witnesses in the four-and-a-half years since this tragic death of Mr. Matthews.”

Leaundra Matthews and Howard are being held in jail without bond.

Wearing a tan jail jumpsuit and a long, white necklace bearing a cross, Lemae Matthews said little during Friday’s court hearing, other than answering standard questions designed to ensure she understood the terms of her guilty plea. Assistant State’s Attorney Patrick Mays read the statement Lemae Matthews gave to prosecutors two months ago,

On the night of the killing, in Montgomery’s Colesville area, Lemae Matthews said, her sister came into her bedroom and asked her to watch her baby while she headed out to pick up Lipford and Howard. “She told me that they were coming over to ‘handle’ Christian,” Lemae Matthews said. “I knew that they wanted to kill Christian but I hoped that they would just beat Christian up instead.”

While her sister was out, Lemae texted and spoke to her by phone. “Leaundra asked me to go to the basement and make sure that Christian was in his room,” Lemae recalled. “I went to the basement and could tell Christian was in his room lying down in bed under a blanket. He appeared to be asleep.”

Lemae Matthews reported that to her sister, and a short time later was told that Lipford and Howard had been dropped off near the townhouse. The men arrived a short time later, Lemae Mathews said, put on disposable gloves and slipped down to the basement.

In previously filed court documents, detectives alleged that Christian Matthews screamed and tried to run upstairs, but Lipford slammed a door to prevent his escape. His shouts became faint, the detectives alleged.

Lemae Matthews said she ran out of the townhouse, still holding the baby, and got into her sister’s car. A few minutes later, she said, Lipford and Howard joined them. “We got him,” they both said, with Howard adding that Christian cried before dying, according to Lemae Matthews’s account to prosecutors.

Leaundra Matthews drove the pair to their friend’s house and dropped them off, according to court records. Lemae Matthews said she wanted to call 911 — hoping that her brother was still alive — but was not allowed to do so until they returned home. When she finally did so, according to her statement to prosecutors, she was vague about what happened because she feared Howard, whom she referred to by his nickname.

“I lied to 911 and the police because I was scared of what Ghost would do if I told the truth,” she said.

Kevin Collins, an attorney for Lemae Matthews, declined to comment Friday. His client was permitted to be released from jail on a $10,000 bond by Judge Jeannie Eun Kyung Cho, who set her sentencing for March 4.

The allegations that one twin went along with the murderous plot of the other twin — even if she didn’t personally agree — is consistent with the behavioral and psychological bonds shared by many twins, Joan A. Friedman, a psychotherapist, author and national twin expert, said in an interview.

“They’re generally in this shared mentality — this kind of us against the world mind-set,” Friedman said. “They don’t question what the other one wants or needs or feels. They don’t think of themselves as individuals. They think of themselves as a pair.”

Friedman suspects the decision made by Lemae Matthews — to agree to testify against her twin sister — was extraordinarily difficult to make.

“They’re usually very loyal to each other, very attached, very secretive,” Friedman added. “Their bond is very strong.”