Jim Litke AP columnist

Of all the cases that might have been thrown out, it’s hard to imagine a tougher defeat for anti-doping authorities than the one that cleared Marion Jones.

Even though it could turn out to be a blessing in disguise. More on that later.

First, let’s talk about tightening the noose. Those same authorities had already busted Jones’ former husband, C.J. Hunter, banned her former companion, Tim Montgomery, the father of Jones’ son, and locked her former coach, Trevor Graham, out of the sport.

Keep in mind that BALCO lab founder and ex-con Victor Conte claimed to be her former supplier.

So when Jones’ “A” sample from the U.S. track and field championships in June came back positive for the endurance-booster EPO, or erythropoietin, it had all the makings of an airtight case.

Then her ’B’ sample tested negative and the bottom fell out.

“I am absolutely ecstatic,” Jones said in a statement released by her lawyers.

Authorities were understandably less enthused.

Losing their biggest fish to date — in the same summer that Tour de France champion Floyd Landis and 100-meter Olympic champion Justin Gatlin got caught — not only raised questions about how the anti-doping sleuths conduct their business. It may have handed the next round of athletes whose results come back positive a ready-made alibi, at least in the court of public opinion.

Said World Anti-Doping Agency boss Dick Pound, “I’m sure there will be some explanation forthcoming from the lab” or from the U.S. Anti-Doping Association. He might be waiting a long time.

Travis Tygart, USADA’s counsel would say only, “We have full confidence in the EPO test, we stay abreast or ahead of the science involved, and we’ll continue using it going forward.”

Drug-testing is always going to be a cat-and-mouse game, with top-shelf chemists and lawyers employed on both sides. Because it relies on cutting-edge science, the results will always be open to differing interpretations. Because the process is modeled on the legal system, everybody gets their day in court.

It may not be perfect, but most athletes will tell you that’s the unexpected benefit referred to above.

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“Like me,” seven-time Tour de France champion Lance Armstrong said in a telephone interview, “Marion has been hit with lots of stuff. But this should remind everybody that at least you get to show up with your representatives and have the test run test again in your presence. That’s the epitome of fairness.

“And if this proves anything,” he added, “it proves that while everybody wants drugs out of sports, there have to be safeguards in place. When I went through something similar last summer, Dick Pound told me over the phone — then he said it publicly, too — he didn’t think a ’B’ sample was always necessary. Well this shows you the police have to be held accountable, too.”

Like Armstrong, former Olympic gold-medal sprinter Jon Drummond stressed the importance of safeguards, but he went a step further. He said it proved that the testing system worked.

“Both WADA and USADA have worked diligently over the past few years trying to clean up sport, and look at the successes they’ve had. That means most of the stories have ended negatively, for the athletes, at least, and few people questioned whether all the procedures were followed or not.

“This story ended positively, as far as I’m concerned, and I’m sure Marion is relieved. So it comes down to how you look at the diamond. Do you see the flaw,” said Drummond, a contemporary of Jones’ on several Olympic teams, “or applaud the diamond? I applaud the fact that the system has worked catching the cheat, and the system also works for those who haven’t cheated.”

For the moment, the people running that system will have to bite their lower lips.

They might be unsettled by the idea of losing one of their strongest cases — and worse, galled by the fact that somebody like Jones, with so many questionable associations, is still running around. And not just running around, but about to return to competition with her career on a definite upswing after two very lackluster seasons.

But they would also be the first to remind that rules are rules.

Win or lose.