07/01/2010 10:15 pm ET Updated May 25, 2011

Why My Friend Got Arrested During the G20 Summit

For 17 hours this past weekend, Toronto police deemed Mark Donald, a 5' 6" bespectacled law student spending his summer working for the Canadian Civil Liberties Association, to be a threat to public order.

All because he happened to be standing in front of the Novotel Hotel on Saturday afternoon, three quarters of a mile away from the G20 summit site, amidst several dozen peaceful demonstrators, journalists and bystanders. He wasn't there to protest anything -- he was an observer, sent by his employers at the Civil Liberties Association to report on whether riot police interfered with demonstrators' legal rights.

It was a job he was well-qualified for, having spent nearly a year prior to law school reporting for print and online media -- it's how we met just over a year ago, when we started work as news analysts at a Toronto-based news magazine.

But nothing prepared Mark for what happened last Saturday evening when, without warning, two teams of riot police surrounded, closed in, and arrested everyone in the group outside the Novotel, Mark with them, on trumped up charges of disturbing the public peace.

From there, Mark was taken to a makeshift jail, where he did not have access to a lawyer, or a bed. Late Sunday afternoon, after protesters massed outside the jail to demand the release of the detainees held there, Mark was released and the charges against him dropped.

Mark's arrest wasn't an isolated incident. More than 900 people were rounded up by police that weekend, including a medical student caught passing by a group of protesters on his way home after studying at a coffee shop, and a 17-year-old girl drawing peace signs on a sidewalk. Police told her she could be charged with possession of a deadly weapon (she was carrying eyewash in her bag).

What made these police officers -- people we assume are in their ordinary lives and work generally rational people -- take leave of their senses and arrest people like Mark Donald?

In 1971, a Stanford psychologist named Philip Zimbardo conducted an experiment. He told 24 volunteers, all college students, that for the next two weeks, they were going to live in a simulated prison. Half were randomly selected to act as prisoners, and the other half were to act as prison guards.

The guards were each given a uniform and a baton. They were also issued mirror sunglasses, which promoted their sense of anonymity and prevented prisoners from making eye contact with them or reading their emotions.

The first day of the experiment passed without incident. But when some of the prisoners began to defy the guards by barricading themselves in their cells and trying to plan a prison break, the guards responded by inflicting increasingly sadistic punishments on the prisoners, such as stripping them naked and firing fire extinguishers into their cells. Within six days, conditions in the "prison" had become so intolerable that Zimbardo decided to call off the experiment.

On some level, the guards must have understood that they were not really prison guards, and that they had no right to abuse the prisoners in the way they did. Yet, over the course of only a few days, they became so immersed in their assigned roles that they lost touch with reality, along with whatever moral code they followed in their normal lives.

I think this experiment helps us understand what happened on the streets of Toronto this past weekend. The police officers were much like Zimbardo's prison guards -- twenty-somethings armed with authority, shielded from the public by riot helmets, almost certainly trained to perceive everyone around them as a threat, and provoked by the torching of several police cruisers by a small sect of anarchists the previous day.

And they responded like those prison guards did -- they became so absorbed in their imagined battle against the protesters that they lost any sense of proportion, charging on peaceful demonstrators and arresting them, and anyone who happened to be around them, en masse.

Police officers' conduct that weekend was predictable, but not inevitable. Neither were the abuses that took place in Zimbardo's prison. In the latter case, they were the result of a situation built and shaped by Zimbardo himself -- he designed the prison, trained the guards, and sat idly by for six days as his prison turned into a madhouse. He is as responsible for what took place there as the guards themselves.

In the same way, when determining who is responsible for what happened in Toronto this past weekend, we need to look to the people who built the situation in which miscarriages of justice like Mark Donald's arrest took place. Who trained the front-line riot police? Who wrote their rules of engagement? Who, if anyone, was assigned to ensure officers did not abuse their authority?

The report Mark helped develop is now available online. It calls for a public judicial inquiry to determine who was calling the shots, who was at fault, and how to prevent mass rights abuses like last weekend's arrests from happening again.

Sounds like a plan.