A police service that failed to keep an informant's identity secret and then failed to take the violation seriously lost

its bid Monday to overturn a $460,000 damages award to the victim and her family.

In siding with the informant, Ontario's top court found Durham Regional Police Service promised Margaret Stack anonymity but went ahead and disclosed her identity anyway.

"If the police tell the witness that they will not reveal his or her identity or involvement in order to get information, they should keep their promise or face the ordinary consequences of violating the assurance they have given," the Ontario Appeal Court said in its unanimous decision. "Simply put: A citizen in Ms. Stack's situation should be able to rely upon what the police tell her."

The case arose when Stack, then of Whitby, Ont., went to police to tell them that a teenaged neighbour had broken into another neighbour's home and stolen some guns, which he took to school and used to threaten other students.

'This is between you and I'

In persuading her to provide the information, an officer promised to keep her identity secret but, without telling her, videotaped their interview at a police station. At the end of the interview, court records show, an officer told Stack: "This is between you and I. That stuff does not get disclosed."

Nevertheless, police gave the video to lawyers for two brothers charged criminally in the case, unleashing a torrent of threatening and harassing conduct by the parents of the accused, court documents show.

The Court of Appeal ruled that the original court finding that a confidentiality agreement was in place was amply supported by the evidence. (Giacomo Panico/CBC)

Among other things, the boys' father drove his truck at Stack, forcing her to jump out of the way. He also told Stack's husband that he intended to pay her back for having gone to the police, and subjected them to ongoing and ultimately unbearable harassment about which police did little, court heard. Stack, evidence shows, felt

hopeless, depressed, anxious and fearful as a result.

Police denied promising confidentiality

"Ms. Stack and her family were so distressed by this conduct that they sold their home and moved to another community," according to court records.

While police denied making any confidentiality promises to Stack, Superior Court Justice Douglas Gray found otherwise. In February 2015, he awarded her $345,000 and another $115,000 for her husband Chad Nissen and their two children.

On appeal, police argued Stack had failed to prove she was a confidential informant and that, in any event, the damages Gray had awarded were excessive.

The Court of Appeal ruled, however, that Gray's finding a confidentiality agreement was in place was amply supported by the evidence.

'Promised confidentiality'

The higher court also rejected police arguments that they had no reason to worry disclosure of Stack's name would put her in any danger because the information she provided was readily available from other sources. The court called that irrelevant. Stack was entitled to rely on the promise of anonymity in exchange for her co-operation, the court said.

"This is a civil case between the police and an individual who was promised confidentiality," the Appeal Court said.

"That promise gave rise to a common law and equitable right entitling Ms. Stack to have her identity kept confidential."

Gray's damages award to Stack and her family for her severe psychological injury was "very generous" but nevertheless reasonable, the Appeal Court said.

The court also ordered police to pay Stack $40,000 for the costs of their failed appeal.