By Arthur Lubow
Updated May 13, 1985 12:00 PM

In comfortable, suburban Orinda, Calif., where the American dream is sometimes taken for granted, Kirsten Costas made adolescence look easy. A 15-year-old sophomore, she swam for the high school team. She belonged to the Bob-o-links, an exclusive volunteer group with sorority overtones. She won a place as a varsity cheerleader. “Kirsten had a good personality,” says Jessica Grant, 16, her classmate at Miramonte High School. “She was pretty and vibrant.” And she was one of Miramonte’s elite.

For Bernadette Protti, life was more of a struggle. An ordinary-looking girl, Bernadette, 15, also belonged to the Bob-o-links. She had good grades and a circle of friends. Yet in the glaring light of her merciless self-scrutiny, Bernadette was a failure. Surrounded by the sons and daughters of highly paid executives, she was embarrassed by the more modest means of her father, a retired public utilities supervisor for the city of San Francisco. She desperately wanted a place on the cheerleading squad. “She worked hard for cheerleader,” recalls Jessica Grant. “She came up to me afterward and said, ‘I didn’t make it and I can’t believe it.’ She was really disappointed.”

About that time Bernadette was also rejected by the selective Atlantis club and denied a place on the yearbook staff—standard teenage setbacks, but to Bernadette they were something more. “Bernadette was accepted and popular in her own way,” says classmate Kris Johnson, 16. “But she had this obsession with being liked. I could never understand why she thought she wasn’t.”

Kirsten Costas probably never thought much about Bernadette. She had no way of knowing that Bernadette was thinking a great deal about her. To Bernadette, the pretty daughter of 3M executive Arthur Costas had become a painful reminder of feelings of failure. “She never liked me…,” Bernadette explained later. “The thing that got me mad was it hurt.” Not that Kirsten ever insulted her. “I mean she didn’t really say, ‘You’re ugly’ or something,” Bernadette remembered. “She just said stuff that made me feel bad.” Once, she recalled, she had been on a school ski trip with Kirsten: “I mean, we don’t have a lot of money and stuff…and I just had this really crummy pair of skis and some boots, but…I was having fun anyway, and she made some comment about them…. It just seemed like everybody else was thinking that, but she was the only one who would ever come out and say that….”

Last June 21, a Thursday, while Kirsten was away at a cheerleader training camp, her mother, Berit, answered a 10 p.m. phone call. The girl on the line knew Kirsten wasn’t home but said she wanted to tell her of a secret Bob-o-links initiation dinner that Saturday night. Kirsten returned home the next day, and on Saturday night her parents and her brother, Peter, 12, attended a potluck dinner for Peter’s baseball team. Berit called home at 8:20 p.m. to wish Kirsten a good time with the Bob-o-links and to remind her to turn on the porch light. It was the last time she would speak to her daughter.

A little more than an hour later, a few miles away, Kirsten rang the doorbell of Alex and Mary Jane Arnold, who had just finished playing cribbage with neighbors. She said she had been with a friend at the church up the road and the friend had “gone weird.” As Kirsten entered the house, Mary Jane noticed someone behind her on the front path—”a gal about 15 with a roundish face and light-brown hair.” Kirsten seemed upset, but not terrified. Unable to reach her parents by telephone, she accepted Alex’s offer of a ride to one of her family’s neighbors. As they left, Mary Jane noticed a small car at the end of the driveway.

When Alex drove off, the car, a mustard-colored Pinto, seemed to be following. He asked Kirsten what was going on. “It’s okay,” she replied. Pulling into Kirsten’s neighbor’s driveway, Alex said he would wait until Kirsten got inside. He watched as she walked to the door, then saw a female figure swoop out of the darkness. He thought he was seeing a fist fight. Then the assailant disappeared in the shadows.

Attorney Arthur Hillman, another of the Costas’ neighbors, was standing at his kitchen sink that night when he heard “a bloodcurdling yell.” Rushing to his front door, he saw Kirsten staggering toward his house crying, “Help me, help me, I’ve been stabbed.” She collapsed into his arms, blood gushing from five stab wounds in her upper body. “She was in shock,” Hillman later testified. “I tried to hold her hand and pray a little on the side.” Returning home a short time later, the Costas family found their normally quiet street clogged with police cars and fire trucks. Then Arthur Costas saw his daughter lying in an ambulance. She was pronounced dead at a nearby hospital at 11:02 p.m.

An hour earlier on that peaceful summer evening, Elaine Protti had suggested a walk when her daughter, Bernadette, returned home in the family Pinto. Nothing seemed out of the ordinary. That summer Bernadette attended classes to prepare for confirmation in the Roman Catholic Church. She swam and saw friends. And she attended Kirsten’s funeral. “I was really good at blocking [what had happened] out of my mind, and I still am,” she said later. “That’s why I can live through every day, because it doesn’t seem real.”

Surprisingly, it took authorities almost six months to find Kirsten’s killer. Local sheriffs conducted more than 300 interviews, investigated more than 1,000 leads and examined 750 Pintos. Many Miramonte High School students were questioned. In the eyes of her classmates, Bernadette was an unlikely suspect. “I knew she had the Pinto, but she was the last person you’d think of,” says her friend Jessica Grant. “She seemed as upset about the murder as everybody else.”

Yet Bernadette’s account of her activities on the night of the murder puzzled investigators. In December she was called back for questioning by FBI agent Ronald Hilley. Hilley reviewed for Bernadette the psychological profile that had been drawn of the murderer. After his description, Bernadette said quietly, “It sounds just like me.” She asked what would happen to Kirsten’s killer. The public humiliation, she said, might be worse even than prison. Then she asked to go home.

Over the next few days, Bernadette committed some of her thoughts to paper. This is what she wrote:

“1. I have caused a lot of hurt and pain to a lot of people….

2. I don’t want to hurt people anymore.

3. I want to go to heaven when I die.

4. I regret what I did.

5. I can’t bring Kirsten back or change time.

6. If I kill myself I will hurt people even more (my family). I think I could kill myself. I would go to hell if I killed myself. I would rather kill myself than go on living if people knew…. Although it’s incredible, my parents are saints who would forgive and love me.”

On the evening of December 10, Bernadette asked her mother, Elaine, if they could have a talk. “I’ll take a nap, but wake me up later,” Mrs. Protti replied. She slept through the night unintentionally and apologized to her daughter the next morning. “That’s okay,” Bernadette said. “I’ve written you a note. I put it on the kitchen counter.” She asked her mother to wait half an hour before reading it. Elaine studied the Bible until the ticking kitchen timer went off. Then she read.

“Dear Mom and Dad:

I have been trying to tell you this all day but I love you so much it’s too hard so I’m taking the easy way out…. The FBI man…thinks I did it. And he is right…. I’ve been able to live with it [for a while], but I can’t ignore it, it’s too much for me and I can’t be that deceiving…. Please still love me. I can’t live unless you love me. I’ve ruined my life and yours and I don’t know what to do and I’m ashamed and scared.”

She added a postscript: “Please don’t say how could you or why because I don’t understand this and I don’t know why.”

Elaine telephoned Bernadette at school and picked her up. “I wanted a last chance with my daughter,” she said later. “I wanted not so much to talk to her but to be with her.” With her husband, Raymond, Elaine drove Bernadette to the sheriff’s office in nearby Martinez where the girl broke down and made a full confession to Hilley. She said that on the night of the murder she had driven to the Costas house and told Kirsten that the Bob-o-links dinner was just a cover story for Kirsten’s parents. What was really happening was a party. According to Bernadette, Kirsten agreed to go but first suggested they smoke some marijuana outside a nearby church. (When the taped confession was played back in court during a three-day hearing in March, Kirsten’s parents gasped in disbelief at the allegation.)

Bernadette said she balked at the marijuana. “We just talked, you know, argued, not argued really, but she didn’t think it was any big deal, and I just didn’t want to, and she made me feel dumb…,” Bernadette told police. “She thought I was being weird.” When Kirsten rushed from the Pinto in the church parking lot, she left behind some marijuana in a plastic bag, said Bernadette, who claimed she flushed it down the toilet when she got home. Bernadette also said she had found the murder knife just by chance—that she had never intended to kill. (Bernadette’s sister, Gina, 25, testified that she often ate lunch in the car while at work, using the knife to cut vegetables.)

After the hearing, Judge Edward Merrill found Bernadette guilty of second-degree murder. She was sentenced last month to a maximum of nine years in the custody of the California Youth Authority and sent to a maximum-security facility near Camarillo. The Costas family, understandably, was hardly in a mood for forgiveness. During the testimony, Kirsten’s mother glared at Bernadette, who sat slumped in a chair while her mother daubed at her daughter’s eyes with a handkerchief, as four of the girl’s sisters stroked Bernadette’s hair and held her hands. “My heart is empty. I ache. I’m half a person,” Berit Costas told the judge before Bernadette’s sentencing. “[She] will probably be given her freedom in a few years…. I ask the people of California, is this justice?”

Some of Kirsten’s classmates agreed it was not. “Whatever happens to Bernadette isn’t going to be enough,” said one. “I’m sorry for her,” said another, “but I still want her to get everything she deserves. She shouldn’t be allowed to forget what she did.” There seems to be small chance of that. “I had dreams about [Kirsten],” Bernadette told Hilley. “I sort of apologized to her in my mind. You know, like I think she’s in heaven now…. I sort of said that I’d still like to talk to her….” For Bernadette, it seems, Kirsten still represents a world from which she herself for so long felt excluded. What has changed is that now Bernadette truly is cut off from that world. And the one person whose acceptance meant so much, the one she so desperately wanted to talk to, has tragically been silenced forever.