Two adults who pleaded guilty to the murder of seven-year-old Katelynn Sampson, who died while in their care four years ago, have been sentenced to life in prison with no chance of parole for 15 years.

Donna Irving and Warren Johnson pleaded guilty to second-degree murder on Tuesday. They had been charged with first-degree murder in the death of the young girl.

In his reasoning for the sentence, Justice John McMahon called Katelynn's murder "brutal, cruel and inhumane."

Irving was the child's legal guardian. Johnson was her common-law husband.

Police responded on Aug. 3, 2008 to Irving's apartment in the Queen Street West and Lansdowne Avenue area. Irving had called 911 and said Katelynn had choked.

Officers noted at the time that the little girl had been covered with marks on her body. One homicide detective said they were the worst such injuries he had ever seen.

The court heard that Katelynn had been taken out of school on May 1, 2008 and was beaten daily in the couple's apartment. She was kept in a room without a mattress and without even a blanket to keep her warm.

She was forced to write lines on pieces of paper found in the apartment. "I have to learn to wash my dishes," Katelynn wrote.

"I am still not listing (sic) and telling the truth," she wrote and, written 62 times, "I am A awful girl and that's why know one wants me."

When she was finally found, Katelynn's hair had been cut off and she had 70 injuries, all over her body. Her cuts were infected and her blood was found in every room of the apartment.

In his judgment, McMahon called the lack of action on the part of the Children's Aid Society and Native Child and Family Services surprising. The court heard earlier in the day that Katelynn's case had been passed between the two agencies, with neither of them responding appropriately.

"The alarm bells were ringing, but no one was responding," the McMahon said. "If someone had, we would not be in this courtroom this afternoon."

Prior to her death, Katelynn had shown up at her Parkdale elementary school with bumps and bruises, but Irving explained the injuries away and everyone seemed to believe her, even when the little girl missed 72 days of school, the court heard.

Bernice Sampson, Katelynn's mother, had surrendered custody of her daughter to Irving in 2007 because she was dealing with her own addiction to crack-cocaine. The two women had been friends for a decade.

Sampson was present in the courtroom on Tuesday as she, along with Katelynn's father and grandmother, delivered victim impact statements.

"I am in pain," read Sampson's statement. "I hurt all the time. They didn't do this to their kids. Why did they do this to mine?"

Mark Letang, Katelynn's father, said: "When Katelynn died I feel like I died. I feel like my soul is bleeding out everyday."

Sampson spoke to reporters outside the court, saying she was happy to have the trial over with.

"I am just happy that Katelynn can rest, and that I can rest, and, you know, that everyone else can rest and that it's over with," Sampson said. "And I hope that it never happens to a child again."

Irving and Johnson read statements to the court, saying they were sorry for their actions, with Irving apologizing directly to Katelynn's mom.

"I'm sorry, I will be haunted by this young child for the rest of my life," Irving said, looking over at Sampson.

Child advocates have noted that no background check had been performed on Irving, who has children of her own, before she was awarded guardianship of Katelynn.

It is possible that the case could prompt an inquest.

With files from CTV Toronto's Tamara Cherry and John Musselman