Toronto police knew Bruce McArthur "had a link" to three of the eight men he pleaded guilty to murdering after interviewing the serial killer in late 2013, according to a newly unsealed judicial order.

The Project Houston task force was launched in November 2012 to probe the disappearances of Skandaraj Navaratnam, Abdulbasir Faizi and Majeed Kayhan, all of whom were connected to Toronto's Gay Village.

About a year into that investigation, police discovered McArthur was connected to all three of those missing men.

The information raises questions about how police handled the investigation into missing men who turned out to be McArthur's victims. In the wake of the 67-year-old's arrest, some in Toronto's LGBT community suggested that police failed to take sufficient action to find the men.

In September 2013, investigators discovered a common link between Navaratnam and Faizi when they found "silverfox51" in both Navaratnam's deleted email contacts and Faizi's notebook, according to the unsealed order.

The cellphone number attached to Navaratnam's deleted email contacts was then traced back to McArthur through a contact card in a police database from when McArthur was caught driving without a valid insurance card in 2005.

That's what led police to interview McArthur on Nov. 11, 2013. As CBC News has previously reported, McArthur was considered a witness at the time of the interview.

Project Houston was launched in November 2012 to probe the disappearances of Skandaraj Navaratnam, Abdulbasir Faizi and Majeed Kayhan, all of whom were connected to Toronto's Gay Village.

In the video interview, the serial killer confirmed that his email address was "silverfox51@hotmail.com." McArthur also admitted to having had a sexual relationship with Kayhan and to being friends with Navaratnam, information that came out at McArthur's sentencing hearing earlier this month.

Going into the interview with McArthur, investigators knew that Faizi had "silverfox51" written in his notebook, but when shown photographs of all three men McArthur told police he did not recognize Faizi.

McArthur still had criminal record in 2013

At the time of the interview, McArthur's 2003 assault conviction would have still appeared on his criminal record, as it wasn't expunged until June 2014.

It's unclear if Project Houston investigators ever did a criminal record check on McArthur at the time of the 2013 interview. If they had, police would have found out that McArthur had assaulted a man with a metal pipe in the victim's home in Toronto's Gay Village.

Given the circumstances, a retired Toronto police detective told CBC News he would have done a criminal record check before even interviewing McArthur.

"He was an important enough witness for them to videotape the statement," said Rolf Prisor. "In all likelihood they did a check on him before they interviewed him so they knew exactly who they were dealing with."

Prisor worked as an investigator through 2004, and says he would videotape interviews with witnesses if he thought they might be lying and would change their story later. He says the video would commit the witness to a position.

In all likelyhood they did a check on [McArthur] before they interviewed him so they knew exactly who they were dealing with. - Rolf Prisor, retired Toronto police detective

The details of McArthur's assault conviction are a "little red flag" for Prisor, but he argues you have to know what other red flags, if any, investigators had at the time.

"You have to be in the detective's shoes more or less to know what he knew at the time, what the extent of their investigation was and what they knew about McArthur," Prisor said.

One discrepancy in McArthur's story investigators might have learned was about the serial killer's connection to Navaratnam. Despite what McArthur told investigators about the two men just being friends, the pair were actually in a relationship sometime in the early 2000s and Navaratnam had worked for McArthur doing landscaping as well.

Police chief won't 'dissect' investigation

Toronto police Chief Mark Saunders refused to "dissect the investigation" when asked Thursday about whether a criminal record check was done on McArthur in 2013.

Instead, Saunders told CBC News he looks forward to answering questions about the investigation at a later date once the appropriate platform is determined.

Right now, it's unclear what that platform will be.

Toronto police Chief Mark Saunders refused to 'dissect the investigation' when asked Thursday about whether a criminal record check was done on McArthur in 2013. (Christopher Katsarov/Canadian Press)

An independent civilian review into Toronto police missing persons investigations is ongoing, run by retired judge Gloria Epstein.

At the moment, the scope of Epstein's review doesn't include the McArthur investigation. But following the serial killer's guilty plea, Epstein asked the Toronto Police Service Board to allow the independent review to examine those cases.

The board's decision is currently on hold as it waits to hear back from Ontario Attorney General Caroline Mulroney about whether or not the province is considering holding its own public inquiry into the McArthur investigation.

Project Houston shut down in 2014

Project Houston was shut down in April 2014 because investigators said they couldn't find any criminal evidence connected to the missing men. The task force originally started when police received a cannibalism tip from a man in Switzerland. As a result, police investigated James Alex Brunton as a murder suspect in the disappearance of Navaratnam.

As previously reported, a number of the judicial orders investigators obtained as part of Project Houston concerned Brunton. In the end, Brunton was not connected to Navaratnam or the other two men, but did plead guilty to child pornography charges.

It would be another three years before a second police taskforce, Project Prism homed in on McArthur again in the wake of victim Andrew Kinsman's disappearance.

McArthur was sentenced to life in prison with no chance of parole for 25 years, after pleading guilty to eight counts of first-degree murder last month.

In addition to Navaratnam, Faizi, Kayhan and Kinsman, McArthur admitted to killing Selim Esen, Kirushna Kumar Kanagaratnam, Dean Lisowick and Soroush Mahmudi.

​CBC Toronto and other media outlets have been in court for nearly a year fighting to unseal information in more than 88 heavily-redacted judicial orders obtained by investigators in Project Houston and Project Prism.

The Crown and McArthur's lawyer had previously argued that the majority of the information in the orders should stay under seal so it wouldn't infringe on McArthur's right to a fair trial.

But the serial killer's guilty plea has made fair trial rights a non-issue. There will be no trial.

Justice Cathy Mocha unsealed the majority of one of the most fulsome judicial orders from Project Prism on Wednesday.

It's from about a week after McArthur was arrested. Investigators were applying for an assistance order, so that forensic anthropologists could examine the Mallory Crescent home where McArthur stored his landscaping equipment.

Police had already discovered human remains in planters on the property and were looking for the help of forensic anthropologists to "investigate and excavate" any other found human remains.

To get the assistance order, police had to lay out details from their entire investigation up until that point. The document is more than 200 pages long.

More information from dozens of other judicial orders from the Project Houston and Project Prism investigations is set to be unsealed in the coming months.