Worse still, their actions are likely to cost us, the taxpayers of this city, a great deal of money.

The authors of this piece meet three times a week to debate the issues of the day on Montreal’s CJAD radio. One of us is progressive, the other conservative, so we don’t agree on much. However, this case is so troubling that we both agree urgent intervention by the mayor is required.

On the day in question, police officers posing as protesters put on masks (in violation of a 2012 municipal bylaw) and infiltrated a small student protest.

The SPVM has confirmed the use of undercover officers, and admitted that one of these officers pulled a gun on a group of unarmed students.

But they have refused to answer questions about two other incidents.

In one of these incidents, a student was physically assaulted in front of journalists, and illegally detained until he had turned over his phone’s passcode so they could delete photos he took of them. He ended the night with a concussion, a sprained wrist and a split lip, in addition to a criminal charge (for intimidation of a police officer, presumably for taking photos) and a ticket for a bylaw infraction. The SPVM have remained conspicuously silent on this incident.

In the second incident, another student was assaulted from behind by a masked man wearing the same clothes as one of the officers involved in the first incident. She was taken to hospital by ambulance and held overnight with a severe concussion and ligament damage to her forearm. The SPVM have denied that the student’s injuries were caused by police intervention but refused to answer other questions about the incident.

Now here’s where it gets costly for us taxpayers. The second student’s name is Katie Nelson, and she was already suing the city, police force and a handful of specific officers for harassment, sexual harassment and political profiling in a lawsuit launched pro bono by well-known constitutional lawyer Julius Grey in 2013.

According to Nelson and another witness the masked officer who put her in the hospital is a named defendant in her case. If true, it raises the question of whether he used his presumed anonymity to settle a personal score, thus demonstrating the exact behaviour Nelson and Grey allege in the lawsuit.

That case goes to trial this summer. If it’s shown that a pattern of harassment has escalated to physical assault, how many zeros do you suppose this lack of impulse control has tacked onto the case’s eventual settlement?

If an ex-boyfriend harassed a young woman for years, and then that harassment escalated to a physical assault that left her in the hospital, he would already be in jail. Nelson, rightly, fears for her safety.

It's all part of a disturbing trend in police behaviour. Emboldened by the lack of consequences for even the most serious misbehaviour, some police officers have decided that they have social licence to physically assault people on the margins of society. Protesting students, homeless people, visible minorities, in short anyone they don’t like.

Our police officers represent us, as a society, on the streets every day. They do a tough job, of that there is no doubt, but that cannot stand as an excuse for illegal and unethical behaviour carried out in our name.

Sadly, the accountability structures within the police force have failed us in this case. It’s time for an external investigation, which should also look at the senior officers who authorized this fiasco.

And for that, the buck stops with Denis Coderre. Our mayor has turned a blind eye to the excesses of this city’s police force for too long. We know you’re busy with the jackhammers and the minion-themed sewer inspections Denis, but it’s time to do your job.

This isn’t about left or right, nor is it about politics. It’s about the rule of law.

Ethan Cox is an editor with Ricochet Media. Tommy Schnurmacher is host of the Tommy Schnurmacher Show on CJAD 800 radio in Montreal.