Open this photo in gallery Brian Greenspan, counsel for the family of Barry and Honey Sherman, provides an update on the investigation into their deaths, in Toronto on Oct. 26, 2018. Christopher Katsarov/The Globe and Mail

The family of slain billionaires Barry and Honey Sherman is offering a $10-million reward in an attempt to “light a fire” under Toronto Police detectives − whose murder investigation, their lawyer says, has been plagued by missteps.

Brian Greenspan made the announcement at a press conference at the headquarters of Apotex Inc., the drug company founded by Mr. Sherman, in north Toronto on Friday afternoon. In the 10 months since the couple was found dead in their north Toronto mansion, Mr. Greenspan has led a team of private investigators in a parallel probe of the killings.

Though he would not offer any details about his team’s findings, Mr. Greenspan had harsh words about “failings and deficiencies” in the police investigation that prompted the family to hire a second set of eyes in the first place.

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“In moving forward, after more than 10 months of silence and frustration, the Sherman family felt it appropriate for the public to understand why they believe that it is time for a new initiative,” he said.

Toronto Police Chief Mark Saunders responded swiftly to the criticism in his own press conference Friday, stressing that police have the same objective as Mr. Greenspan and his team, and insisting the case has been handled with “a high level of professionalism.”

The bodies of Ms. Sherman, 70, and Mr. Sherman, 75 - whose net worth was estimated to be $4.77-billion - were discovered on Dec. 15.

Their 12,000-square-foot home was up for sale, and real estate agents made the gruesome discovery by the indoor pool in the basement. The bodies were clothed and in a semi-seated position, hanging, side by side, from belts tied to a railing. Mr. Sherman’s legs were outstretched in front of him, with one crossed over the other, Mr. Greenspan revealed Friday, “wearing his undisturbed eyeglasses and his jacket pulled slightly behind his back which would have prevented use of his arms.”

It should have been obvious, Mr. Greenspan said, that they had been “staged postmortem in a very deliberate manner.”

Yet that same evening, a police officer told reporters outside the home that there were no signs of forced entry, and that they were not looking for any suspects. Members of the Sherman family were outraged by the statement − which Mr. Greenspan said they believed compromised the integrity of the investigation.

He was retained by the family the next day and quickly assembled a team of private investigators, including several retired Toronto Police detectives.

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The team hired Dr. David Chiasson, retired chief forensic pathologist for Ontario, to conduct a second autopsy of the bodies on Dec. 20 − which Mr. Greenspan said made clear they had been murdered. The findings were offered to Toronto Police, who did not meet with the pathologist until Jan. 24.

In the meantime, Mr. Greenspan said, police had indicated in court filings that they were investigating the murder of Ms. Sherman alone.

Two days after the meeting with Dr. Chiasson, Mr. Greenspan noted Friday, Detective-Sergeant Susan Gomes of Toronto Police announced at a press conference that they would be investigating the deaths as a double homicide. When Mr. Greenspan’s team took custody of the Shermans' home that same day, it became clear that “best practices were not followed by police.”

For example, he said they failed to vacuum the crime scene for hairs or fabric particles, or conduct a thorough examination of the homes’ locks.

“If this best practice had been followed, they would have located a point of entry to the home which would have seriously undermined their misleading and irresponsible conclusion that there had been no forced entry,” Mr. Greenspan said. “The police also missed at least 25 palm or fingerprint impressions that were discovered by our private team at the scene once the house had been turned over to us after more than six weeks on the scene.”

Fingerprints and DNA they did collect, he said, have yet to be identified.

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Despite his criticisms, Mr. Greenspan stressed that their objective is not to audit the police. The reward, he hopes, will light a fire under both potential tipsters and detectives. A 24-hour tip line has been set up at 1-833-668-0001 for North American callers, and 011-905-849-7373 for international callers. Mr. Greenspan said all leads will be analyzed and vetted, and any meaningful information will be sent immediately to Toronto Police.

He has appointed three experts to sit on a panel to assess the eligibility of tipsters for the reward and invited Chief Saunders to appoint an officer to join them.

He said they have also proposed a broader partnership with police, which they have not accepted. Asked whether such an arrangement would ostensibly create a two-tiered system for the wealthy, Mr. Greenspan argued the contrary; that it would free up resources for the homicide unit during a particularly taxing year. There have been 88 homicides in Toronto so far this year. There were 65 last year.

“While the lifestyle or position which a victim held in society should never have a bearing on either the public resources or the commitment which investigators have in solving the crime, it is also understood that investigations of this nature are complex and time consuming,” he said.

In his press conference Friday, Chief Saunders dismissed the allegation that his detectives reached any premature conclusions.

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“The investigation was done well and it continues to be done well," he said. "But I do want to say that it’s not over yet.”

Asked specifically about his officer’s statement outside the home on Dec. 15 that there were no signs of forced entry or suspects, he said the officer’s goal was to ease the fears of neighbours in the affluent area, after a previous rash of break-and-enters.

Chief Saunders said he supports the family’s decision to post a reward but he said that this is not always a successful tool. He said he would welcome the partnership, as long as the conditions withstand the scrutiny of the law.

“If it meets the test, then we will definitely be involved,” he said.