As courtroom theater, it was devastating: First, chief deputy D.A. Birgit Fladager, the new lead prosecutor in the Scott Peterson trial, played a home video of Laci Peterson for the jury. Then, on Sept. 29, she introduced into evidence a gauzy blouse that Laci wore the night before she vanished. Fladager asked jurors to pass the blouse around; as they did, a few broke down in tears. Up until then they had only seen still photos of Laci. "When Birgit took over, she's showing us videos of Laci as an alive, warm human being," says Bay Area defense attorney Daniel Horowitz. "Then she comes in with Laci's blouse. The jurors handled it almost as if they were touching Laci—as if they loved her."

With that humanizing masterstroke, as well as her sharp questioning, Fladager, 43, revived a four-month prosecution that has often seemed to falter. She was brought in to close, and so she did: The state rested Oct. 5. Fladager had been supervising senior deputy district attorneys David Harris and Rick Distaso—so why step in now? The D.A.'s office won't say, but Horowitz suggests "the prosecution was afraid it was going to lose." Surely the defense will stress that Fladager still has scant physical evidence against Peterson. That hasn't stopped her in the past. In 1999, for instance, she won a conviction—absent physical evidence—against computer expert Douglas Mouser in the strangling death of his 14-year-old stepdaughter. Says his attorney, Richard Herman: "Birgit has what is important to any trial attorney—believability."

Fladager is the youngest child of four born to Myles, 72, a retired Navy captain and lawyer, and wife Phyllis, 70, a homemaker. In 1986 she graduated from McGeorge School of Law in Sacramento, where she met husband Stephen Critzer, an assistant clerk recorder. The couple, who have no children, served as Navy lawyers, then in 1990 Fladager joined the Stanislaus County D.A.'s office. "She's not one you'd ever want to underestimate," says her brother Kenneth, 48, a prosecutor in Albuquerque. "She has a knack for getting what she wants."