ON CAMERA, Marla Olmstead is one of the cagiest abstract expressionist artists ever interviewed. Olmstead makes a chronically tight-lipped painter like Jackson Pollock seem like a chatterbox. Facing queries about her work habits, the meaning of her paintings or her technique itself, she demurs and tries to turn over the microphone to her brother. When pursued by questions she would rather not answer, she retreats inside the round of her skull and gives the camera wide yet shut-off eyes and a thin, enigmatic smile. Even at 4 years of age, Olmstead knows the right way to deal with the press.

The documentary My Kid Could Paint That is not, I stress, a mockumentary, even though the subject matter is hard to believe. Director Amir Bar-Lev tries to crack the case of the precocious artist, whose canvases sold for many thousands of dollars on the New York art market. Instead, it is Bar-Lev who ends up cracked, baffled by two contradictory propositions. One is that Marla is a genius who can't be seen at work, whose true creative process is as hidden from view as Schrödinger's Cat. The second is that Marla is the point-child in a delicious fraud that hoodwinked the usual authorities: The New York Times as well as serious connoisseurs beguiled by the notion of a pure child working in the cynical and egomaniacal art world.

Maybe we should take Marla's guidance and concentrate on the art. They are good paintings, whoever did them. Trying to make an abstract painting is an instructive process. After such an attempt, one tends not to echo the philistine comment Bar-Lev uses as his title. Moving paint around is a technical challenge; making the paint do what you want takes time and learning. The canvases we see toward the film's end are the work of someone with a fine sense of color, depth and motion. They have some value outside of the hysteric and status-driven art market. But is it all a fraud? 60 Minutes 2 suggests so, causing a huge crisis in the Olmstead family. The broadcast spurs a flurry of disgustingly vicious hate mail. They're aimed at Marla's apparently guileless mom, Laura, a dental hygienist, and father, Mark, the night manager at a Binghamton, N.Y., Frito-Lay plant. There is a whiff of rat here: Mark does some figurative painting and is seen urging Marla on (is he coaching her?). And Marla keeps insisting that her little brother, Zane, does paintings as well.

Among the interviewees are the first person to write about Marla, Elizabeth Cohen of the Press and Sun Bulletin. In Cohen, Bar-Lev finds the best and most reliable perspective on this mystery. One feels for Bar-Lev, who went in as a innocent and ended up as forlorn as Albert Brooks expelled from the family unit in Real Life. Meanwhile, this utterly fascinating and (naturally) colorful enigma gives one as much to talk about as any movie this year. On a simpler level, one is charmed by the little artist, as well as by the soundtrack: some vintage Nino Rota and Dylan's perfectly placed "When I Paint My Masterpiece."

MY KID COULD PAINT THAT (PG-13; 82 min.), a documentary by Amir Bar-Lev, opens Oct. 12 at Camera 12 in San Jose and the Aquarius in Palo Alto.

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