The country's top court has agreed to hear appeals from three murder convicts and a convicted fraudster who claim their trials were tainted by jury-vetting.
It has not been decided yet whether the Supreme Court of Canada will hear the cases separately or together, but either way they will be watched closely in jurisdictions across the country after the Ontario trials and a similar one in Nova Scotia reached opposite conclusions.
In separate cases spanning three years, Ontario's top court ruled that the fact police had quietly done background checks on prospective jurors did not affect the trials of the defendants.
The rulings - the most recent coming last October - appeared to contradict one last July in which Nova Scotia's appeal court ordered a new trial for a man convicted of operating a marijuana grow-op because the jury had been vetted.
In that case, the court found the jury selection process was unfair and had given prosecutors an unfair advantage.
The Supreme Court of Canada has now agreed to hear the cases of Ibrahim Yumnu, 48, of Wasaga Beach, Ont., and Vinicio Cardoso, 39, of Toronto - both convicted in 2005 of killing a Barrie, Ont., couple - and the cases of Troy Davey, 21 of Cobourg, Ont., convicted in 2005 of killing a police officer, and James Emms, 45, of Barrie, convicted in 2008 of fraud.
They were among almost a dozen verdicts under appeal in Ontario over the checks, which also spawned an investigation by the provincial privacy commissioner almost two years ago.
Privacy commissioner Ann Cavoukian issued an order telling prosecutors to stop collecting personal information on would-be jurors beyond the allowed check for a criminal conviction.
Eighteen of the province's 55 Crown attorneys' offices had gathered personal information on prospective jurors since 2006, when the attorney general finally issued a memo ordering an end to the controversial practice, first raised in 1993.
Normally, background checks can be done on prospective jurors to ensure a criminal conviction has not rendered them ineligible to serve on a jury, a process Ontario's appeal court called "logical."
However, because information on jury candidates is bare-bones, police also accessed databases that went beyond revealing criminal records.
In the cases of Mr. Yumnu and Mr. Cardoso, the court found the prosecution did not actively disclose the vetting.
However, the Crown and judge made references to the screening during jury selection and police notes indicating the officer had conducted the checks were turned over to the defence at trial.
It was only during the appeal, which initially centred on the judge's charge to the jury, that the defence argued the convictions were tainted because the Crown had secret information that allowed it to pick a favourable jury.
"The defence did nothing, for over four and one-half years," Justice David Watt wrote for the appeal court. "They are disentitled to any relief now."'