Congressional hearings once famously informed the nation that Oliver North’s lawyer Brendan Sullivan was not a potted plant. For all their masquerading as showcases of bloviation and indignation on demand, those hours-long inquiries that only a C-SPAN junkie could love have on occasion yielded worthwhile disclosures. In the 1980s, onetime White House secretary Fawn Hall admitted to smuggling classified documents from the Old Executive Office Building in her boots.

In the 1990s, the Clarence Thomas Supreme Court confirmation hearings provided a rude image involving a Coke can – but forced a serious look at sexism. And earlier this year, then-Attorney General Alberto Gonzales demonstrated a memory as blank as the 18.5-minute gap in the implausibly erased Nixon White House tapes.

But what good can come from members of the House Oversight and Government Reform Committee trying to pry more credible revelations from the likes of Roger Clemens, Brian McNamee and Kirk Radomski than former Sen. George Mitchell and his steroids investigators already did?

Despite Chairman Henry Waxman’s aggressive nose for fraud, do we really expect him to uncover the truth about whether Clemens took steroids in his big backside, as his former trainer McNamee claims and the Cy Young-winning pitcher denies?

The biggest truth from this same committee’s 2005 hearing featuring Mark McGwire, Sammy Sosa, Rafael Palmeiro and Jose Canseco was that taxpayers weren’t going to get truth for their money. We still don’t know whether McGwire did or didn’t do anything harder than andro, a legal substance not banned by baseball until three years after he retired.

Palmeiro’s claim that he never used steroids was contradicted five months later when he was suspended for a positive drug test. Canseco, who has ‘fessed up to steroid use, told one of his many shifting stories that day. Credible or not, he turns up in Mitchell’s report, having “told members of my investigative staff that he had numerous conversations with Clemens about the benefits of Deca-Durabolin and Winstrol and how to ‘cycle’ and ‘stack’ steroids.”

That 2005 circus is credited with pushing Major League Baseball to take abuse of performance-enhancing drugs seriously. But Mitchell says that Commissioner Bud Selig asked him to undertake his investigation after a pair of reporters (then with the San Francisco Chronicle) published the book “Game of Shadows” in 2006, examining allegations that Giants home-run king Barry Bonds used steroids.

So where’s a baseball fan supposed to find truth? According to the Mitchell Commission, McNamee says he injected Clemens with steroids and human growth hormone in 1998, 2000 and 2001.

“Absolutely false and defamatory,” Clemens says in a lawsuit filed this week in Houston – against McNamee but, curiously, not against Mitchell.

Mitchell’s report says McNamee talked under threat that he could be charged with a felony if he lied. Clemens’ suit says McNamee was threatened with prosecution if he didn’t implicate Clemens – a subtle but distinct difference.

Clemens growled on CBS’ “60 Minutes” and snarled at a news conference, as though to intimidate skeptics – like when he threw that broken bat toward Mike Piazza hustling to first base.

But will members of Congress stare him back down when he and others appear, now in February? (Mitchell, Selig and players union rep Don Fehr are set for Tuesday.) If they merely blink in the glare of so much starpower, they’ll have wasted not just time but an opportunity to help force performance-enhancing drugs out of professional sports.

That’s important, not just for players’ health or the integrity of fair competition but for the message it sends to young athletes. Pressures to get bigger, faster and stronger to gain an edge are inherent in competitive sports at all levels. As long as performance enhancers are accessible to the pros without sufficiently serious penalties, they’ll trickle down to the amateurs. And to those tempted to cheat, safeguards such as mandatory testing will look like mere temporary roadblocks to behavior that’s ultimately destructive.