Betty T. Threatt, 27, is expected to appear Monday in court and enter into a plea deal. (Bonnie Jo Mount/The Washington Post)

When the mother dropped her 9-year-old son off at his father’s Washington home last June, the father was struck by the appearance of the boy, whom he had not seen in about a year. The child appeared to be malnourished. He had bruises and burn marks, and there were bits of duct tape stuck to his wrists and ankles, his father later told social workers.

Taurus Bulluck, 30, rushed his son to Children’s National Medical Center. Doctors determined the boy had 60 injuries, according to D.C. Superior Court documents. They called police.

Police said that over a period of three months, between March and June 2014, the boy’s mother and her then-boyfriend kept the child locked in a bedroom in their Southeast D.C. apartment as “punishment” for misbehaving. The mother later told police she was “embarrassed” because the boy has cerebral palsy, according to court papers. She also said she “hated” her son and blamed him for a miscarriage, the papers said.

The mother, Betty T. Threatt, 27, is to appear Monday before Judge Rhonda Reid Winston in D.C. Superior Court, and her attorney said in court that she intends to enter a plea deal with prosecutors. Neither side would discuss details of the agreement. Her former boyfriend, Lester O. Jackson, 52, rejected a plea offer and is to go to trial in July.

Court, police and social service documents, along with family interviews, present a harrowing tale of how the boy allegedly ended up locked away without anyone noticing. Bulluck told social workers that Threatt had stopped allowing him to see their son. When ­Threatt moved to the District from Prince George’s County in February 2014, she failed to enroll him in school, according to two officials with knowledge of the case. The boy’s grandmother said she eventually became so worried that she called social services.

Threatt, Jackson and their attorneys would not comment publicly, and Bulluck did not return repeated calls and messages left with family members.

Threatt told social workers that she was born to a mother who was addicted to crack cocaine, an allegation her mother declined to address. At age 9, Threatt was sent to an inpatient psychiatric facility for treatment after putting the family cat in a microwave and turning it on, according to social services documents. “I got meds for my anger and therapy,” she told a court-appointed psychologist recently. She said she was diagnosed with bipolar disorder.

Threatt said that a year after she returned home, she was raped by her mother’s boyfriend, an allegation that her mother denies. By the time she was 13, Threatt gave birth to the first of her five children.

‘I thought I could trust her’

The boy was the second-oldest of Threatt’s children. For the first few years of his life, he was raised by Threatt, his father and his paternal grandmother in Bulluck’s family home in the 300 block of Decatur Street NW. Threatt, Bulluck would tell a social worker, “moved in and out” of the house several times during the boy’s early years, then finally left for good, leaving Bulluck and his mother to raise the boy.

When his mother died in 2013, Bulluck told social workers, he felt he could no longer care for his son and sent the boy to live with ­Threatt. “I thought I could trust her,” Bulluck told a D.C. social worker, according to a 28-page document prepared on Oct. 23.

Bulluck said he visited his son at Threatt’s apartment on weekends for a year, according to the report. But Bulluck lost contact with Threatt after she began dating Jackson and eventually moved, according to the social services report. Threatt would not give him her new address, he told social workers, and allowed him to speak with his son only with the phone on speaker.

As 2014 wore on, Bulluck became more concerned about his son’s whereabouts, according to the report.

He told a social worker that Threatt told him she had sent the boy to live with his maternal grandmother. The grandmother, Lora Brighthaupt, 56, said in an interview that it wasn’t true. She said she, too, became worried about the boy last year.

In February 2014, Threatt and Jackson moved with the boy and his three younger siblings from Temple Hills, in Prince George’s, to the District. Police said that soon after the move, the couple began locking the boy in a bedroom and withholding food.

According to the police charging document, Threatt received about $700 a month for her son as part of his government disability check. She told social workers she also received about $732 a month in Social Security for her disability.

Threatt told police she had Jackson change the locks on the boy’s bedroom so it locked from the outside, according to the charging documents. She also told authorities that she struck the boy with a belt and that she and Jackson wrapped the boy’s ankles and wrists with duct tape, the documents state.

Sometime over the next few months, Bulluck and Brighthaupt both began searching for the boy, according to Brighthaupt. “I hadn’t seen my grandson in four months. My family hadn’t seen him. There had to be something wrong,” she said.

Brighthaupt said she contacted D.C. Public Schools but got no answers. She said she and Bulluck later went to a school where she thought the boy was enrolled. “They would not allow us to come in the building and check and see if he was there,” she said.

Eventually, Brighthaupt said, she called the D.C. Child and Family Services Agency. A spokes­woman for the agency declined to comment on whether an investigation was launched.

Bulluck would later tell a social worker that he thought Brighthaupt’s call prompted Threatt to drop their son off at his home on June 18.

After her arrest a few days later, Threatt’s three younger children, ages 1, 4 and 7, were placed in foster care. It is unclear who had been caring for her oldest daughter. A neglect case has been filed against Threatt involving the younger children.

More than a week in hospital

When the boy was 5, he was diagnosed with cerebral palsy, which mostly affected his left hand, according to the social worker’s report. After her arrest, Threatt told a detective that she was “ashamed” of her oldest son. Social workers did not detail any signs of physical abuse of Threatt’s other children.

Prior to her arrest last June, Threatt had little contact with police. In 2009, D.C. Superior Court records show Threatt was arrested for driving without a license. In 2012, she was arrested for assaulting her landlord and was ordered into anger management classes.

Threatt’s family blames Jackson for the alleged abuse. “My daughter wasn’t like that until she met” Jackson, Brighthaupt said. “She wasn’t into drugs. She didn’t drink; she didn’t do nothing. I’m not saying it was anybody’s fault. I’m just saying my daughter was not like that before she met that man.”

Threatt’s sister, Asia Brighthaupt, 30, said, “It was the man, the dude my sister was with, who made her do those things.”

Jackson, who has a 1-year-old with Threatt and adult children ages 34, 27 and 22, told a social worker that he and Threatt dated for about four years and that the relationship was “up and down.”

In 1992, Jackson was arrested for handgun possession. The outcome of that case is not clear. Prosecutors also allege that Jackson, while in the couple’s apartment, pulled out a handgun, pointed it at his head in front of Threatt and the children and said he would pull the trigger.

The boy, now 10, spent more than a week in the hospital, where he was treated for his injuries and monitored by the psychiatric unit. “Mr. Bulluck was practically living at the hospital with his son, attending team meetings, attending therapy session (both physical and mental) to learn how to care for his son post-discharge,” the social worker wrote.

Later, the child received therapy, working on walking long distances, climbing stairs and his speech.

A teacher told a social worker in October that the boy, now in the third grade in a Southeast elementary school, was “clingy” and that there was some concern about his performing at grade level. But overall, the teacher said, the boy was “doing well.”

The boy’s grandmother said he was “excellent” and likes football and basketball. “He doesn’t talk about what happened,” Brighthaupt said.

Bulluck told social workers that he is now focused on raising his son.

“It’s all about school, video games and getting back to normal,” he told the social worker.

As for what police say happened with his son’s mother, “I will teach him to respect her, because she is his mother, but never to forget,” he said.

Julie Tate and Jennifer Jenkins contributed to this report.