Within hours Whispel confessed, and described how the threesome came up with a gruesome plan out of the blue.
"I was sitting in Denny's with Adam and Valessa, and I heard something about killing her mother, and I was, like, there's no way we could actually do something like that," Whispel recalled.
Whispel told detectives it was Davis who had come up with the bizarre plan of how to kill Vicki Robinson: "We went back to the house, got the van and tried to go down to get some heroin for an overdose."
But Whispel said he didn't really believe Davis was serious, even after Davis tried to buy heroin and couldn't find any. Shortly after midnight, they returned to Valessa's house, where her mother was asleep.
They went to Valessa's bedroom, Whispel said. The three teens had taken LSD earlier in the evening. There, Davis came up with another idea of how to overdose Vicki Robinson: bleach, according to Whispel.
About that time, Valessa's mother woke up and came into her bedroom. "She was, like, 'Valessa, get your sleeping bag and go sleep in my room,'" Whispel recalled. "Mrs. Robinson turned around from the doorway and walked into the kitchen. Adam followed her out there."
"I didn't know if he was going to turn on me if I would have said something," Whispel added.
Whispel then described the last few moments of Vicki Robinson's life. And in chilling detail he blamed most of the murder on Valessa's boyfriend, Davis.
"All of a sudden...you could hear a pin drop," Whispel said. "And the next thing we hear is choking, struggling noises. Me and Valessa, we look at each other and we run out to the kitchen. We seen Mrs. Robinson sitting on the ground, and Adam had her...in a choke hold. She was coughing and, you know, struggling, trying to get away," he recalled.
"Adam was trying to take the syringe and stick it in her neck," he added.
Whispel handed Davis a knife, then returned to Valessa's bedroom, Whispel said. "Valessa came in sat down next to me and all of a sudden I hear this, like, escaping-of-air breath type of noise from the kitchen," Whispel said. Vicki Robinson was dead.
Once Whispel confessed, Davis agreed to give his own description of what he did to Robinson.
"I started raging 'cause I was tripping so hard, and John brought out the knife. He said, 'Here use this,'" Davis declared. "And I don't know how I did it; I don't even remember what was going through my mind when I did it; but I just sliced.
"And we put her body in the trash can and started cleaning up the blood," Adam said.
They then loaded Robinson's body into her van and drove to a wooded area behind Whispel's house, according to Davis. "We put her down a trail and covered her up with some dried up palm trees."
According to Whispel, Valessa just sat in the van and watched.
What they did next disturbed investigators almost as much as the crime itself: After stealing Robinson's van and her money, they went on a spending spree, buying clothes, drugs and tattoos.
After their confessions, Davis and Whispel were charged with first-degree murder. Valessa Robinson was being held in a different facility, in a juvenile detention center in Odessa, Texas. When Valessa told her version, detectives were stunned: Valessa claimed Davis and Whispel didn't kill her mother; she did it alone.
Declared Valessa: "I had pinned her down, before I, like, stabbed her; I had to pin her down. I had stabbed her in her throat, and she wasn't dead yet, and so I stabbed her again twice in her back." Valessa was also charged with first-degree murder.
But aftre a few months alone in prison, away from Davis, Valessa claimed her boyfriend, Adam Davis, killed her mother while she was high on LSD in her bedroom. The only thing Valessa said she's guilty of is not rescuing her mother. And for that, she had no explanation. "I hate myself that I didn't save my mom," Valessa said.
Where did Valessa's troubles start? Valessa's sister Michelle says the problems started when Valessa was 11, and her parents divorced. "My sister took the divorce very hard; she changed a lot when that happened," Michelle said.
After the divorce, Valessa didn't see much of her father, Chuck Robinson. He moved out of state in search of a new sales job. Valessa was devastated about her parents' breakup and missed her father, because he was her biggest supporter.
Her mother also wasn't around much, according to Valessa's friend, Christie Collins. Vicki Robinson had a new job as a real estate broker and a busy social life. Valessa and Michelle recalled how Valessa didn't fit in at school, and was teased.
At 12, Valessa had been allowed to join a rock band with men in their 20s. She began experimenting with drugs. In eighth grade, she started skipping school and doing more drugs. "Acid was the main thing that we did; we also did Ecstasy," Valessa said. She started staying out all night.
"I don't know what Vicki could've done differently," said Vicki's new boyfriend, Jim Englert, who said that Valessa was beyond discipline.
Then something happened during the summer after Valessa's eighth grade that Valessa's father says may have been a turning point. Vicki Robinson and Englert took a two-week family vacation to Michigan, and when Valessa refused to go, Vicki Robinson just left her young daughter behind, alone.
"I thought it was unconscionable. I thought it was nuts, said Chuck Robinson. For two weeks, Vicki Robinson never called to check on her daughter. Valessa was 14.
Shortly after that Valessa met 18-year-old Adam Davis, who was living on the streets. His father was dead and his mother had abandoned him when he was 2. He was a high school dropout and a drug dealer. They developed a devotion that bordered on obsession. "Looking back, I realize that he had this overwhelming control over me," Valessa said.
Why didn't her mother try to stop the relationship? Valessa explained: "She was afraid that if she stepped in and put her foot down and said you're not seeing this guy anymore, I think she was afraid I would leave. And I probably would have."
Finally Vicki Robinson took action. Without telling Valessa, she made plans to send her daughter to a yearlong program for troubled teens called Steppin' Stone Farm.
But 10 days before Valessa was scheduled to start a program at the Steppin' Stone Farm, Vicki was murdered.