TORONTO -- Warning: This story contains details that may be disturbing.

The Toronto detective who investigated the brutal murder of Katelynn Sampson says that when he heard the 911 call reporting her death he immediately knew something didn't add up.

Seven-year-old Katelynn Sampson was beaten and murdered by her guardians in 2008, but no one bothered to check on the girl when there were obvious signs of abuse. 

CP24's crime analyst Steve Ryan was the lead homicide detective on the case at the time. 

"This was one of the worst cases I investigated in my 15 years in homicide," Ryan said in this week's episode of The Detective. 

Ryan was called to the Parkdale apartment after a 911 call from a woman named Donna Irving. She told the operator that the seven-year-old had choked on chicken soup and bread and was dead. 

"[Paramedics] are trained professionals and they can detect child abuse," Ryan said. "I think they suspected right from the get-go that this child did not die as a result of choking on chicken soup," Ryan said. 

Katelynn Sampson

A year and a half before her tragic death, Katelynn's mother gave her daughter to Irving to care for her, while she battled a serious addiction to crack cocaine. 

"I had a serious problem, so I made her go to Donna," Beatrice Sampson told reporters after her daughter was murdered. "I thought we were friends. We were friends for almost 10 years."

The courts and child services agreed that Irving would be Katelynn’s permanent guardian, never checking that Irving had a criminal record and two of her own four children had been seized by Children's Aid.

"Her injuries were some of the worst I've seen," Ryan said. "Let's start with her hair. Her head was shaved and we learned later that was as a result of punishment. She had beautiful long hair in some of her pictures. That was hacked off, she looked like an army recruit."

Ryan said there was ongoing punishment in the second-floor Toronto apartment where they lived.

Katelynn Sampson is seen in this undated file photo.

Investigators found a notebook with this line written 62 times: "I am a awful girl, that is why no one wants me."

Ryan says the autopsy showed the child’s liver had disengaged from her body from the severe beatings. He said he had only seen that in traffic collisions, never in a child abuse case. 

Katelynn's eyes were swollen, one swollen shut.

"She was underweight,” Ryan said. “She had not been fed, and she would have been in excruciating pain, according to the pathologist, and her finger was sliced. It wasn’t cut, it was sliced in an odd spot right at the base, almost at the web of the finger and when you look at that injury in and of itself, you can’t help but think that was done as punishment because it was an odd place for the injury to have happened.”

The cause of death was determined to be complications from a variety of different injuries, mostly blunt force trauma. 

"Basically how it was explained to me is that her body just said 'We've had enough, we're checking out, the injuries just too severe for her to continue.'"

The 911 call came at 2:30 a.m. with Irving crying on the line.

Donna Irving, charged with second-degree murder in the death of Katelynn Sampson, is seen in this court sketch.

"My daughter, we were in the bedroom, I was in the bedroom and she was eating bread and she choked and she is dead."

Ryan later found out Irving had a shower and a beer before dialling the emergency number. Her actions would lead the investigators to think something just wasn’t adding up. 

"With most homicide investigations, what I try to do, is get to the 911 tape as quickly as we can to listen to it to get some idea or feel for the investigation."

This investigation would be no different and immediately Ryan had concerns that this was not a real cry for help. 

"On that tape she is crying, I hesitate to use that word because it was all concocted, but she is making it appear as though she’s crying. Now in fairness she may have been crying for her own self preservation because she is now stuck with this body in her apartment and they have a story in place that is not going to be believable," Ryan said.

Irving's common-law partner, Warren Johnson, claimed he was not in the apartment at the time Irving made the call, but Ryan says they found security video from the building showing Johnson leaving with her two children shortly after the 911 call is made. This would lead the investigators to charge both with second-degree murder. 

For this week's episode of The Detective, Ryan went back to the scene of the crime. He said that this is the first time he's been back since 2008.

"There are certain cases you just never forget. Obviously, this is one of them, it has a tremendous impact on your life in general, the after effects of doing this type of work. So being here again, it is tough because all those emotions come back, all those injuries on that child's body, all of what we worried about in terms of this investigation, all comes back when you walk through these doors again."

With Katelynn's body removed, the investigators obtained a search warrant for the apartment. It would take just minutes to conclude this was no accident, it was murder. 

"So when we executed a search warrant on that apartment, there was blood in the bathroom," Ryan said. 

It didn't make sense that Irving had told police she had taken a shower and yet there was blood on the floor. 

"That is where I believe she died, in that bathroom. In the bedroom, there was a hockey net and there was a bowl of chicken soup," Ryan said.

And it would get worse for the seasoned cop as he would learn more about the horrible world this helpless girl was living in.

"If you saw the extent of her injuries, you would understand why she hadn’t been seen by anybody."

Her school was right across the street from her building, but for months prior to Katelynn's murder, she had not been to class. 

Nobody checked up on her.

"And that is ironic, and I think about it to this day. You look at how close the school is to where she lived. Donna would call the school to say Katelynn is not feeling well today, she fell off her bike, there were all kinds of excuses and that was it, it is a 30 second walk if that, to go bang on her door. If someone knocked on Katelynn’s door she would be alive today. There is no doubt in my mind, but nobody checked on her at all."

Irving and Johnson both pleaded guilty to second-degree murder and are serving life sentences. But after their convictions, an inquest was held into how Katelynn fell through the cracks, her case bounced between Children’s Aid and Native Child and Family services. 

The former director of the latter says much has changed.

Katelynn Sampson Funeral

"It has improved in so far as there is much more formality in exchange of information, duty to report is clearer, technology associated with sharing information is there, there is an integration in the database with respect to child welfare agencies," Ken Richard said.

He said the biggest change is that different agencies now communicate with each other in a much better way. 

"At the time of Katelynn’s death, there was a history of three different child welfare operations involved and not necessarily communicating very well with respect to what they were looking at so there have been technical improvements. I think that duty to report with respect to all professionals with children, seeing children in distress, is much more understood and emphatic, so we have a tighter, tighter safety net. That being said, it is never tight enough."

Just next to the front doors to Parkdale Public Junior and Senior School, there is a memorial to Katelynn. 

She can be seen in a large picture smiling with long hair in a pony tail. At the time Ryan visited the area, someone had put a birthday greeting on the door. It is reminder to anyone entering the building that there is a duty to follow up and report suspected child abuse.

"Because what allowed Irving and Johnson to beat this child like they did, was the fact that nobody checked on her. Had any of these teachers, principals, janitors, I don’t care who it was, anyone in this school who realized we haven’t seen her in months and she is always having unusual injuries appear out of nowhere and this is why she is not in school, had someone gone across the street she would have been alive."