The case was solved in December 1984, and a classmate named Bernadette Protti was arrested.
Click here to read more of the story, which later became the (fictionalized) subject of not just one but two TV movies — “A Friend to Die For” and “Death of a Cheerleader.”
Orinda girl stabbed to death
Oakland Tribune – Monday, June 25, 1984
Contra Costa County Sheriff’s deputies were searching yesterday for a teenage girl as a suspect in the stabbing death of another girl here Saturday night.
Sheriff’s deputies said Kirsten Costas, 15, was stabbed repeatedly after she was given a ride home by a Moraga resident, who was not identified.
Last hours of Orinda teen’s life
San Francisco Examiner newspaper headline from June 25, 1984
Police said today 15-year-old Kirsten Costas thought she was going to a sorority-like initiation the night she was stabbed to death just a few yards from her Orinda home.
Teen suspect sought in cheerleader’s death
(Continued from article above)
Witness surfaces in teen murder
The Californian, Salinas, California – Monday, June 25, 1984
A popular 15-year-old girl who was stabbed to death on a neighbor’s doorstep may have been the victim of another teen-age girl, police said.
Teen-aged girl stabbed to death
Santa Rosa Press Democrat – Monday, June 25, 1984
High schooler stabbed in Contra Costa
Roseville Press-Tribune – Monday, June 25, 1984
A popular 15-year-old high school cheerleader described as an “All American girl” was stabbed to death on a neighbor’s doorstep, apparently by another teenage girl.
Kirsten Costas, who had just finished her sophomore year at Miramonte High School in this scenic, affluent suburb, was killed at about 10pm Saturday, Contra Costa County Sheriff’s Department investigators said.
The only apparent witness to the killing told reporters that he and his wife were playing pinochle in their home with neighbors in nearby Moraga when Kirsten, looking frightened, came to their door and asked to use the phone to call her parents.
The witness, who declined to be identified, said Kirsten was with a friend who had started to “go weird” he said.
READ MORE: The real death of a cheerleader story (1985)
Slain Orinda teenager was lured, police say
Oakland Tribune – Tuesday, June 26, 1984
A teenage girl sought in the stabbing murder of an Orinda cheerleader lured her victim from home under the guise of driving her to a phony initiation ceremony for a socially-exclusive volunteer group, Contra Costa Sheriff’s deputies said yesterday.
Meanwhile, deputies continued to hunt for a “chunky,” “stringy-haired” teenage girl suspected in the slaying of 15-year-old Kirsten Costas, a well-liked cheerleader and swim team member at Miramonte High School in Orinda.
Sheriff’s aide Michael Bachman searches for murder weapon
Stunned friends wonder why Orinda girl was killed
San Francisco Examiner – Tuesday, June 26, 1984
Police and friends are still perplexed about a brutal killing that so far has no suspect or motive — only a pretty and popular 15-year-old victim.
Sheriff’s investigators have only leads and a description of the woman suspected of stabbing Kirsten Marina Costas to death Saturday night, but not much else.
Another Orinda girl may have gotten invitation to phony dinner
The Petaluma Argus-Courier – Tuesday, June 26, 1984
Young friend mourns Kirsten
San Francisco Examiner – Thursday, June 28, 1984
Hundreds bid sad adieu to Kristen at emotional rites
San Francisco Examiner – Friday, June 29, 1984
Hundreds of mourners filled the great sanctuary of the Lafayette-Orinda Presbyterian Church yesterday to pay their last respects to Kirsten Costas.
More stood in the narthex, craning to hear the service in memory of the 15-year-old Miramonte High School student, stabbed to death near her Orinda home Saturday night.
The killing, which has left authorities baffled, occurred as the popular student and cheerleader was apparently fleeing a bogus invitation to an initiation dinner for the “Bobbies,” a public service sorority-like group she had joined.
Reward offered for Orinda teen’s killer
The San Francisco Examiner – Wednesday, July 4, 1984
Cops hunt leads in girl’s killing
The Oakland Tribune – July 6, 1984
Hundreds of calls have come in on a special 24-hour hotline, but investigators said yesterday they have no leads in the June 23 killing of 15-year-old Kirsten Costas.
“A number of people have called saying they think they have seen the suspect. Other people have called saying they have feelings about people who might be the suspect. There have also been psychic calls. The calls have come from all over,” Lt. James Robinson said.
Reward reaches $15,000 for slayer of Orinda girl
Oakland Tribune – July 11, 1984
Parents of slain girl end seclusion
Oakland Tribune – Wednesday, September 5, 1984
All leads fail in slaying of teenager
Oakland Tribune – Saturday, October 6, 1984
Four deputies working full-time, and two more working part-time, have followed 800 separate leads without finding a clue in the murder of Kirsten Costas, the Orinda high school sophomore slain June 23.