The guardians of Katelynn Sampson have pleaded guilty to second-degree murder in the seven-year-old's beating death and been sentenced to life in prison with no chance of parole for 15 years.

Donna Irving and Warren Johnson were responsible for the care of the little girl when she died in the summer of 2008.

Irving, 33, and Johnson, 50, pleaded guilty to the charges.

On Aug. 3, 2008, police found Katelynn inside an apartment at 105 West Lodge Ave., in the Toronto neighbourhood of Parkdale, with obvious signs of trauma. Veteran officers described her injuries as the worst they had ever seen.

Irving had called 911 and said the girl had choked on some food and was not breathing.

On Tuesday, details of the girl's death were read out in court for the first time.

The autopsy revealed 70 external and internal injuries including bruising, contusions, abrasions, lacerations and fractures to virtually every part of Katelynn's body. The medical report said the injuries were so severe it would have made it painful to move her lips, talk, eat or drink.

As the court heard the details of the abuse, the girl's mother, Bernice Sampson, started sobbing uncontrollably and was helped from the courtroom by Mark Letang, Katelynn's father.

When given the opportunity to address the court, Irving claimed that Katelynn’s death has haunted her.

"I wish it happened to me, not to her," Irving said in court.

"I can’t sleep without seeing Katelynn’s face. For the rest of my life, that girl will haunt me."

However, Bernice Sampson said Irving's words do not amount to an apology.

Katelynn Sampson died in 2008 at the hands of her guardians. (CBC)

"I regret it every day, that's what happens when you trust your friends," she said outside the court. "I'm just happy that Katelynn can rest and I can rest."

Girl's injuries 'horrific'

In passing his sentence, Superior Court Justice John McMahon said Katelynn's injuries could only be described as "horrific, brutal and inhumane."

Katelynn ended up in the care of Irving and Johnson because Sampson, had given her friend Irving custody of her little girl so she could clean up her life after she had been charged with drug trafficking.

Irving and Johnson did not react and sat with their heads lowered as the court was told that when emergency crews arrived they couldn't tell whether they were treating a boy or a girl because Katelynn's head had been completely shorn of hair.

The paramedics observed "significant" trauma to the child, including external blunt force injuries to Katelynn's scalp, face, torso and extremities.

A later examination of the Parkdale apartment by forensic investigators turned up more evidence of abuse.

They "located Katelynn's blood in every room — in closets, and in the main hallway, on surfaces including walls, floors, doors and furnishings. A plastic baseball bat [was] stained with Katelynn's blood," reported the CBC's Lucy Lopez from the court.

Investigators also found a book, titled The Devil's Chimney, stained with Katelynn's blood.

Inside the book Irving wrote, "Katelynn is the devil's child because she never listens. She smells bad because she never has a bath. Katelynn has died eyes, and a died soul [sic], heart, and brain."

The autopsy also found 30 scars to multiple areas of the girl's body.

Evidence showed Katelynn had been to see a doctor 34 times up until the age of six with no health problems or bruises. Her mother took her to a doctor for the last time in 2007.

All of the child's injuries occurred after she was prematurely taken out of school in May 2008 while she was in the care of Irving and Johnson. The couple's two boys had no injuries or bruises.

The autopsy found Katelynn did not die from choking but from complications of multiple blunt force injuries inflicted by one or both of her guardians.

News of the discovery of her battered body sparked outrage. Ontario Premier Dalton McGuinty later promised to examine how the courts handle child custody cases to provide better protection of vulnerable children.