In this court, you'll laugh with conviction

But first, ladies and gentlemen of the jury, we have the first act. It starts off well enough, in the middle of a trial - facts and charges never quite explained - presided over by a judge who's taken a few pills too many. Mamet has fun with the legal jargon, the cast has fun with the contrast between absurd ideas and sober phrasing, and the audience has fun with all of it.

Then, however, we get two separate scenes of the lawyers outside the courtroom: the Defense Attorney counseling the Defendant, and the Prosecutor at home with his lover, Bernard (the only character who gets a name instead of a label). Defense Attorney lets slip an anti-Semitic barb, Defendant counters with a few degenerate-priest jokes; Prosecutor and his "Bunny" conduct a stereotypical hissy fight. Each scene escalates to a crescendo of cliches, aiming to draw the kind of laughter that comes between gasps - laughter not because something's truly funny, but because we're seeing someone who has the audacity to say or do outrageous things.

And, sure enough, Mamet gets his laughs; he also gets what he may be even more interested in, a bit of reflection on whether some of these ethnic and religious jokes really do seem funny to the audience and on why some do and some don't. Mostly, though, I found myself reacting as I do when a toddler keeps saying "poop": The first time I might laugh because he knows he's being ridiculous; I might even laugh the second time because the situation is truly absurd. But by the third time, at most, I'm ready for something new.

Fortunately, in Act 2 Mamet supplies it. We're back in the courtroom, and when the judge comes scurrying in after a recess he's more disheveled, more exhausted, and even funnier than before. Where the first court scene was amusing, this one is over-the-top hilarious. The judge pops pill after pill - only for allergies, and yet they seem to induce a kind of manic hysteria - as the Defense Attorney, the Prosecutor, the Defendant, and even the Bailiff follow him ever upward, ever louder, ever looser, in a widening spiral of demented glee. By the time Bernard shows up with a suitcase, the incongruity hardly even registers.

It's also in this act that we realize with full consciousness what had been tugging at our brains in the first scene, and what in fact we had almost articulated many times before but had never quite seen with such clarity: Will LeBow is one of the funniest human beings on the planet.

I kept scribbling down lines that his addled Judge was delivering, but in staring at my scrawls I can see that just quoting the lines will do nothing to convey the sheer, bubbling delight produced by LeBow's delivery of them. It's the way he arches an eyebrow, tilts his head, allows just the tiniest and most timely pause - it's every little gift of comedy, and it's something that you just have to see to enjoy.

Thomas Derrah and Jim True-Frost are also quite fine, and often quite funny, as Prosecutor and Defense Attorney, respectively, though Scott Zigler's direction lets them reach too hysterical a pitch too quickly; a little more sanity would throw the eventual insanity into sharper relief. Remo Airaldi has less to do as the Defendant, but he does it with a dogged thoroughness that's entertaining in itself.

But it's LeBow, literally and metaphorically perched above all, who presides. Ladies and gentlemen, let us all rise.

Louise Kennedy can be reached at kennedy@globe.com.