Until a parliamentary subcommittee stepped in to look into the matter, the government had deployed a lot of heavy legal artillery to prevent Colvin from telling his story to a more private inquiry held by the independent Military Police Complaints Commission.
Why?
From the Prime Minister on down, the Conservative government has always claimed it was unaware of detainee torture at the hands of the Afghan authorities, at least until a case surfaced in 2007, prompting a belated review of the detainee transfer protocol.
But Colvin's narrative makes it clear the government could not have been in the dark about the potential prevalence of torture unless the country's top civil servants conspired to keep their political masters out of the loop, and that is highly unlikely.
As of 2006, Colvin – who was serving in a senior official position in Afghanistan – was sending scores of reports warning of systematic detainee abuse. At first they seemed to fall on deaf ears. In time, he was asked to deliver them only verbally.
There is no evidence those instructions stemmed from a lack of confidence in Colvin's professional judgment or in the information he provided.
He is currently posted at Canada's embassy in Washington as a senior intelligence officer.
The embassy is hardly a backwater on the Canadian diplomatic circuit. It is not the kind of venue where rogue officials are normally posted until they can be quietly put to pasture.
According to Colvin, the clampdown order came from the very top, from officials who reported directly to Prime Minister Stephen Harper or his ministers, often on a daily basis.
In 2006 and 2007, the Afghan file was not only Canada's most important military engagement in decades; it was also the Prime Minister's self-chosen defining foreign policy file.
Moreover, Harper had come to office purporting to make human rights a more significant cornerstone of Canada's foreign policy, a notion he missed no occasion to spell out in public and, presumably, in private.
At the time the Conservatives took power, the public service was still reeling from the fallout of the Gomery inquiry into the sponsorship scandal. By and large, federal mandarins were determined to take all available steps to avoid getting tangled up in a partisan chain of command again.
It would have been an astounding decision on the part of the senior civil service to keep its Conservative masters out of any critical loop on the Afghan file.
In the House Thursday, Defence Minister Peter MacKay did not say the government had not been apprised of Colvin's reports. Instead, he dismissed them as lacking in hard evidence and implied that they were based on Taliban propaganda. It is hard to ascertain how Harper or his ministers could have come to such a definitive and contrary conclusion from their Parliament Hill offices. Colvin, among others, was supposed to be their eyes and ears in Afghanistan
His testimony comes at a time when Canada's military deployment in Kandahar is starting to wind down.
Given the heavy toll of the mission and its ambiguous results, some form of comprehensive post-mortem was already very much in order.
The latest developments make that even more of a necessity.
The Gomery commission was set up for much less cause than a suspicion of high-level wilful negligence of Canada's human rights obligations.
Chantal Hébert is a national affairs writer.
