Boston Marathon bombing suspect Dzhokhar Tsarnaev won’t be sent before a military tribunal for a technical reason: As a U.S. citizen, he isn’t eligible.

But that technicality stopped us from addressing a more important consideration: Even if authorities could bring the terrorist before a military commission, why would they ever want to?

By coincidence, Tsarnaev was read his Miranda rights Monday — the very day the marquee defendant of the military tribunal system, Khalid Sheik Mohammad, was supposed to have had a pretrial hearing at Guantanamo Bay. But that hearing was postponed by two months after it was revealed that somehow hundreds of thousands of defense emails had — oops! — wound up in the files of the prosecution.

That outrage was just the latest snafu in a military tribunal system that has careened from disaster to fiasco over the last dozen years. This comedy of errors has been thoroughly documented in a new book by Jess Bravin, the Wall Street Journal’s Supreme Court correspondent.

“The Terror Courts: Rough Justice at Guantanamo Bay,” makes compelling arguments that, compared to civilian trials, the military trials take longer, cost more, have inferior procedures and produce more lenient sentences. Forget the ideological and legal debates over the military tribunals: The things just don’t work.

Bravin writes that, after 9/11, the Bush Justice and Defense departments and the CIA saw no need for a new military system to try terrorists.

Rather, “commissions were conceived and championed by officials whose primary motive was redistributing powers from the legislative and judicial branches to the executive,” Bravin writes. Obama wanted to end that pointless system but “was persuaded that his political capital was better spent on other priorities.”

The Bush administration’s chutzpah and Obama’s cowardice left us with the absurd arrangement we have today.

Of the 800 people to pass through Gitmo, Bravin reports, there have been all of seven convictions in the tribunals: five plea bargains and two trials, only one of which was contested. The trials cost the government hundreds of thousands of dollars per week (judge, lawyers, witnesses, journalists and all the rest must be flown to the base in Cuba, where some sleep in tents) and produce questionable outcomes.

David Hicks, an Australian who was the first to be sentenced by a terrorism tribunal, got a nine-month sentence in addition to time served in Gitmo; he is now a free man and wrote a book about his experience. Compare that to John Walker Lindh, tried on similar charges in civilian court because of his U.S. citizenship. He got a 20-year sentence.

The prosecution of Khalid Sheik Mohammad and his co-defendants had a kangaroo-court feel even before the defense emails mysteriously wound up in prosecutors’ hands. As my Washington Post colleague Peter Finn reported, microphones had been hidden in rooms where defense lawyers met with their clients.

At another point, a large tranche of defense lawyers’ files disappeared from the military computer network they were stored on.

Confidence in the integrity of the system is so low now that defense lawyers have resorted to filing handwritten motions and communications. There have also been problems with mistranslations by interpreters and uncertainties about which laws applied to the proceedings.

There should be little wonder, then, that it took nearly a decade for Mohammad to be arraigned. First, the CIA kept him at a black site prison where he was waterboarded 183 times, Bravin recounts.

After the Supreme Court’s ruling in the Hamdan case in 2006, the Bush administration had to shut down the prisons and transfer Mohammad to Guantanamo Bay — but concerns that details of torture would be made public slowed the prosecution.

In 2008, Mohammad tried to plead guilty, but under military rules he wasn’t allowed such a plea to a capital charge. More delays came when the Obama administration tried to transfer him to civilian courts, then retreated after a public backlash.

By the most optimistic forecast, the military trial could start sometime next year — 11 years after his capture.

And some would have had us put the Boston suspect into this black hole? That’s nuts — not because the military tribunals are unconstitutional or unfair, but because they’re unworkable.

Dana Milbank is a columnist for The Washington Post. He can be contacted at danamilbank@washpost.com