Last Thursday, a woman who witnessed a fellow passenger on the Canada Line being groped took a photo and uploaded it online with a plea for the victim to come forward to transit police.
Transit Police Service spokeswoman Anne Drennan says the "See Something Say Something" campaign encourages passengers to report suspicious behaviour to police, but posting photos or videos of the activity on the Internet isn't helpful.
"We would prefer that it not be posted because it may influence somebody one way or another," she told B.C. Almanac's Gloria Macarenko.
Wade Deisman, a criminology professor at Kwantlen Polytechnic University, says it's not yet known how common incidents of citizens sharing photos or videos of crimes has become. Despite people's good intentions, such "virtual vigilantism" can be dangerous for a number of reasons, he said.
Victims have to relive trauma
"The fact is, if you have a video that goes viral that shows somebody being victimized time and time again, that's a devastating consequence for that person," Deisman said.
"It's humiliating for them and it's a kind of re-victimization."
Trial by public opinion
"We have a system of justice in Canada that's evolved according to the principle of due process, which means innocent until proven guilty, the presumption that person will get fair trial," Deisman said.
"The victim has rights, too, to decide what disposition they have towards experiencing the criminal act."
Encouraging reports can lead to false positives
Deisman gives the example of the FBI, which began a campaign after 9/11 where they asked citizens to phone in with tips about people who they thought could be terrorists. They received two million calls in the first week, said Deisman.
"It was a massive waste of resources and manpower to try and investigate all those calls, and the vast, vast, vast majority of those calls turned out to be not useful at all," he said.
"Some were revenge calls, some were just wild goose chases."
To hear the full interview with Anne Drennan and Wade Deisman, click on the audio labelled: The dangers of virtual vigilantism.