She was a runaway, a 16-year-old castoff who landed on the streets of Portland with pigtails and a country twang, spinning a hard-luck tale to anyone who'd lend an ear. Her name was Brianna Stewart, she said, from Mobile, Ala. Her mother died when she was 7. She was searching for her long-lost father and struggling to forget sexual abuse at the hands of a sinister Navajo stepdad.

Even though she looked old for her age, several families at the Glad Tidings church in Vancouver, Wash., took her in. She enrolled at Evergreen High School as a sophomore, went to the homecoming dance with a classmate, and earned a GPA of 2.85.

As time went by, however, Brianna's stories grew increasingly outlandish. She said she'd been the high priestess of a Satanic cult run by her stepfather. A Midwest U.S. senator had gotten her pregnant while she was working on his re-election campaign.

After graduating from Evergreen and weaving a convoluted web of false accusations, she wound up in court, where prosecutors said she was actually Treva Throneberry, a 32-year-old woman from Electra, Texas, who had been sexually molested as a child.

The world has no shortage of impostors. They do it for the money, or to escape the law, or sometimes for the sheer thrill of the masquerade. Their alter egos usually crumble at the first challenge.

But Brianna's case was harder to understand. First, she had no clear motive. Second, she managed to hoodwink a platoon of professional skeptics--including cops, lawyers, reporters and teenagers. Third, despite a mountain of evidence identifying her as Throneberry--including fingerprints, DNA tests, dental records and photos--Brianna never wavered from her story. Not even from her jail cell. Not even when prosecutors offered her a deal to spend only four months in jail if she admitted faking her identity.

Brianna refused the deal. She was convicted of perjury and theft, and sentenced to three years in prison. In June 2003, she was released from the Washington Corrections Center for Women in Gig Harbor. She moved to Seattle and lived for several months at Noel House, a women's shelter run by the Archdiocese of Seattle.

She continues to maintain that she is not Throneberry. Last year, she told Primetime Live that the FBI had screwed up the fingerprint match. As for the DNA tests, she claimed that the Throneberry family had "altered blood" as a result of chemotherapy, which had thrown off the tests.

She was last spotted by KATU reporter Dan Tilkin outside Seattle's Westlake Center, sporting pigtails and bib overalls, telling passersby that she's an abductee, an amnesiac, a runaway--anything but the girl from Electra.