And CBC News has learned the other two pillars of military justice — the directors of defence and prosecution — have each also apparently broken military regulation for a similar failure.
Cathcart, the military's judge advocate general, has admitted he failed to provide reports on the administration of military justice, as he is required to do by law.
Not complying with the National Defence Act or military regulations could be violations of the code of service discipline.
Those reports are supposed to be made public by the defence minister tabling them in Parliament, and they're a key access route to information about the military justice system for members of Parliament, Senators and the public.
The reports discuss the status of the military justice system. They describe important cases, priority legal work, trends in law and details of the work and workload of those who work in the JAG system. More crucially, the reports also lay out important statistics about the number and type of charges and the disposition of cases.
But two other senior military lawyers appear to have also not filed their own mandatory reports.
Strict code of conduct
Col. Mario Léveillée, director of military prosecutions, and Col. Del Fullerton, director of defence council services, have each also apparently not filed their own annual reports to Cathcart.
In each case, the last reports published were in 2009-10.
The military on Thursday was unable to say whether reports for the following years had in fact been written, but just not published. If so, it would raise questions about why the judge advocate general hadn't filed his reports when his subordinate commanders had.
All three lawyers could find themselves being held to account by the military justice system they each help administer.
All lawyers, military or otherwise, follow a strict code of professional conduct.
Those codes require lawyers to observe all laws, work diligently and act with integrity and honour. A failure to follow the code of conduct can result in counselling, sanction or disbarment.
Power limited when it comes to public officials
Cathcart is a member of the Nova Scotia Barrister's Society. He has also received the coveted legal designation Queen's Counsel — a title that honours lawyers who demonstrate exemplary service to Canada's legal system.
The executive director of the Nova Scotia Barrister's Society, Darrel Pink, told CBC News that he would examine whether Cathcart is in violation of any of the society's rules.
Pink said he would have to determine whether Cathcart's three-year failure to file his annual reports amounts to a violation of the code of professional conduct. He'll also have to examine whether Cathcart's conduct can be excused, as he is not just a lawyer, but also a public office holder.
"The code of conduct applies to all lawyers regardless of where they practise," Pink said. "But, our jurisdiction is ... circumscribed when the behaviour that is brought into question is as a public official and not as a practising lawyer."
Cathcart holds a public office created by law and is appointed by the minister of national defence.
The Nova Scotia Barrister's Society has specific rules for public office holders that require them to "adhere to standards of conduct as high as those required of a lawyer engaged in the practice of law."
A parliamentary committee quizzed Cathcart on Tuesday about the missing reports.
Cathcart later told reporters he had not failed to live up to his obligations, saying he "wouldn't characterize it that way."
Cathcart said he was not just the superintendent of military justice but also the government's lead adviser on military law matters. All that work, he said, required him to set priorities and consequently the reports were let slip.
"So with the resources and the priorities that I have at my disposal, I made those decisions and I made them knowing full well the gravity of those decisions," he said.
The most recent report on military justice covered the 2010-11 year, but was only tabled in Parliament in March.
A spokeswoman for Defence Minister Rob Nicholson said the minister has now requested the JAG work to get those reports filed "on an expedited basis."
'Part of his obligation'
Ottawa lawyer Paul Champ has worked on human rights cases involving the military. Champ said Cathcart has obligations it appears he hasn't fulfilled.
"He's not simply a public office holder, he's an officer of the court and a lawyer," Champ said. Filing those annual reports "is part of his obligation.
"The most senior legal official in the military is now flagrantly in breach of the National Defence Act, that’s very troubling. I'm stunned.”
Champ became well-known in political circles after he represented Amnesty International and the B.C. Civil Liberties Association in a case that featured allegations of the transfer by the military of Afghan detainees to the risk of torture in Afghan prisons.
Champ said there are generally too few mechanisms for the public to have oversight of the operations of the military. He said it's imperative the military fulfil the few transparency obligations it has — especially those mandated by law.
Champ wondered why neither Defence Minister Rob Nicholson nor Peter MacKay before him demanded Cathcart file those reports on time. Both men are lawyers and would have understood the law.
Only insight into courts
"If the minister sees that the superintendent of military justice is not respecting the law, then I guess the minister feels it's not so important either," Champ said.
The soldier-turned-lawyer Michel Drapeau has been aware of the missing reports for some time.
He's a co-author of one of the definitive texts on military law. Drapeau said he's been waiting for those reports in order to include recent military justice statistics in an updated version of his book.
"It's incredible," Drapeau said. "I don't have access to the stats and we have no idea whether it's good or bad or whatever. These reports are the only way we know what is going on inside military courts."
The question of how charges would arise against the three officials is problematic. For instance, who would decide on charges against the director of military prosecutions? After all, it is his job to decide whether charges go ahead.
"The only thing they can do ethically is resign," Drapeau said.