Investigative journalist Andrew Mitrovica had a fine cautionary commentary in Tuesday's Toronto Star.

An excerpt:

The headlines were disturbing. "Terror Suspects Plotted in Toronto." "CN Tower Threatened."

I didn't pluck these ominous headlines from weekend newspapers blaring word of the police case against 17 alleged "terrorists." They were written three years ago by scoop-thirsty papers announcing another suspected cabal of terrorists plotting mayhem and murder in Toronto.

The news stories accompanying the headlines quoted seemingly unimpeachable documents and conveniently anonymous intelligence sources that provided chilling "details" of the nest of terrorists conspiring in our midst.

The "revelations" were repeated by other news organizations in a never-ending loop. There appeared to be little effort to independently verify the information, just reflexive regurgitation from journalists who are supposed to be involved in a craft that is founded on curiosity and skepticism.

The headlines and allegations turned out to be untrue. There was no cabal of terrorists and certainly no plan to attack the CN Tower. What there was, however, were damaged reputations and futures. Individuals who were named in these news reports effectively had the word "terrorist" stamped on their foreheads.

That stain is hard to erase.

Editors and reporters at news organizations would do well to remember this cautionary tale and the litany of other cases where Canadian citizens or landed immigrants — mostly Muslim men — have been similarly accused of being terrorists.

Journalists also need to remember that their first responsibility is to vigorously question the official version of events, not simply repeat it as gospel.