Bensonhurst, Brooklyn, 9:20 p.m. A young woman plops herself in the backseat of the cab. She's not a happy customer. Her name is Leah, she's locked out of her apartment, and she has to go to her boyfriend's to pick up her extra set of keys. In a voice that grates on the eardrums, she recounts her love life to the driver, Carl Velloza, who appears unusually interested. This boyfriend is not her first. She was engaged at 16 but called it off. She's an ''old-fashioned girl,'' though she doesn't need a man.
One wonders whether she'd be flapping her gums like this if she were aware of the video equipment recording her every word. Five lipstick-size cameras are hidden near the visors. Buried within the seat cushions and roof of the car are enough microphones to outfit the Secret Service. A van loaded with audio and video gear trails the cab. Inside, filmmaker Joe Gantz peers intently at a monitor, hanging on Leah's every word. Through a radio he pipes questions into a hidden earpiece worn by the taxi driver. When the ride ends, Gantz turns to his three cohorts in the van and announces, ''Leah's a B. She was a good talker, but it was all surface.''
Over four weeks last summer in New York City, Joe, 40, and his brother Harry, 36, captured 600 such conversations on tape and selected 11 to produce Taxicab Confessions, a one-hour special that airs Jan. 14 at 10 p.m. on HBO (and repeats four times during the month). Among the Confessions: A man recounts how the death of his wife led to his homelessness. A woman justifies her work as a prostitute. A beautiful lesbian tries to entice her female cabbie to come home with her. A cop describes the times he's seen people hit by subway trains. An old Jewish man breaks out his violin and serenades his driver with ''Sweet Georgia Brown.'' The encounters make for startling, riveting television, and Taxicab Confessions promises to be one of the first TV sensations of the new year.
Confessions isn't the Gantz brothers' first foray into cinematic voyeurism. In 1987, the two produced a PBS docu-soap, Couples Arguing (no staged spats allowed), and they are now seeking airtime for Runaways, conversations with wayward children. ''The media follows celebrities around like a dog with its nose in the butt of another dog,'' says Joe, whose straitlaced appearance belies his intensity. ''But there are a lot of other things to sniff out there.'' Some may question the invasive nature of his documentaries, even though he gets signed releases from everyone he puts on the air. But Joe sees nothing wrong with his recent cab-ride eavesdropping. ''It's not spying. We're not scandalizing these people. We're showing them as they really are.''
On an evening last July, Joe Gantz loaded his van and rigged Carl's cab for a final night of trolling for titillating conversations.
9:43 p.m. ''We got a live one!'' says Carl, one of the eight real cabbies selected from 200 applicants. The prey, Todd, is a lanky 17-year-old who needs a lift to the Palladium, a Manhattan nightclub. Joe directs Carl to turn the conversation around to sex.