The scars and bruises on Justis Burland-Arnett's battered and lifeless body left little doubt that the 6-year-old had been systematically mistreated when his caretaker brought him to Lake Region hospital nearly two years ago. The only question was whether the woman charged in his death would be held responsible.

The answer came Thursday in Otter Tail County District Court when Bobbie Christine Bishop, 42, pleaded guilty to second-degree murder just over a week before she was scheduled to be tried on a host of related charges.

Bishop and her partner, Walter Henry Wynhoff, 46, were charged in April 2018 with five felonies ranging from malicious punishment of a child that caused great bodily harm to second-degree murder, without intent, while committing a felony. Wynhoff pleaded guilty in March to second-degree manslaughter and is serving a four-year sentence. He agreed to testify against Bishop, if required.

Bishop said in family court filings that the mother of Justis and his twin brother had given up their parental rights years ago. She said that Justis and his brother were taken in by their grandmother, Norma Burland, of Polson, Mont., but that she could not handle them. Bishop told investigators that she had agreed to care for the boys. Bishop later moved with them to Fergus Falls, according to a police statement.

Wynhoff told investigators that Bishop cared for the boys around the clock, and that she sometimes whipped them with a belt when they soiled themselves. She also taped Justis to the wall at times, he said. Physicians noted ligature marks on Justis' body.

Thea Rothmann, a court-appointed psychologist, examined Bishop and concluded that she was incompetent to stand trial.

According to the court filings:

Bishop said she dropped out of school in the eighth grade. She said that she has dyslexia, severe allergies, asthma and seizures. She said she has never held a job and that she was beaten during a 13-year marriage that ended in divorce. Bishop's mother said Bishop has always had a hard time understanding things, and that she had to accompany her to medical appointments.

Psychiatric tests showed Bishop's nonverbal and verbal comprehension levels equal to that of a 5- and a 7½-year-old, respectively. And she has an IQ in the "extremely low percentage range of .01, indicating 99.9% of her peers would perform better on assessment."

State prosecutors demanded a review. Kristin Matson, a forensic psychologist, observed Bishop for a month and retested her, concluding she was deliberately misrepresenting her cognitive abilities.

Bishop's attorney, Brian Geis, contended that she lacked a rational understanding of her rights, the charges against her, and the possible consequences of a conviction.

In October, Judge Barbara Hanson ruled that although Bishop has a mental deficiency, she was competent to stand trial. Sentencing is March 20.