Background
The daughter of affluent parents, Arthur and Berit Costas, she and her brother, Peter, grew up in the small suburban town of Orinda, California.
The daughter of affluent parents, Arthur and Berit Costas, she and her brother, Peter, grew up in the small suburban town of Orinda, California.
Costas attended Miramonte High School, and was a member of the school"s varsity swim team and the cheerleading squad.
On June 23, 1984, Costas was lured with a phony invitation to a dinner for the Bob-o-Links, a sorority-like group at school. According to Protti"s later testimony, she had planned to take Costas to the party to befriend her, but Costas got angry when she was told that there was no dinner for the new "Bobbies". At the Costas home, Arnold, sitting in his car, saw Protti attack Costas.
He thought that he was seeing a fist-fight but, in fact, Protti stabbed Costas five times with an 18 inch Butcher knife and fled.
The Costas" neighbors called an ambulance, but Kirsten was mortally wounded and died at a nearby hospital. lieutenant took the police almost six months to find Costas" killer.
After Protti passed a lie detector test, her alibi went unverified. After attempting to confirm Protti"s alibi and rereading her lie detector test, the police knew that the girl had lied.
After speaking with an Federal Bureau of Investigation officer, who informed her that her arrest was imminent, and that they knew she killed Kirsten, Protti wrote her mother a letter in which she made a full confession.
The Costas did not believe Protti"s story – they claimed that nobody would use an 18-inch-long (460 mm) knife to slice tomatoes and that Protti, casually dressed on that evening, never intended to take Kirsten to a party, but had planned to murder her. Protti was sentenced to a maximum of nine years, but was released seven years later on parole. The Costas family left Orinda and moved to Hawaii.
Bernadette Protti was released from prison in 1992 at the age of 23.