Jamie Silvonek, 14, pleaded guilty Thursday in the death of her mother, Cheryl L. Silvonek, in their Upper Macungie home.

Silvonek pleaded guilty in Lehigh County Court to first-degree murder, criminal conspiracy, abuse of a corpse and tampering with evidence and was sentenced to 35 years to life in state prison.In April 2015, Silvonek, who has been held in the Lehigh County Jail, was charged as an adult in the death of her mother, a 54-year-old Jim Thorpe High School graduate.Silvonek's boyfriend, Caleb Gregory Barnes, 21, was charged with homicide, abuse of a corpse, tampering with physical evidence and criminal conspiracy. Barnes' case is scheduled for trial on April 11.Cheryl Silvonek's body was found buried under dirt and snow in the 5700 block of Haasadahl Road in South Whitehall Township on March 15, 2015. Coroner Scott Grim determined the cause of death to be multiple stab wounds to the neck.An autopsy also showed that the victim had contusions, abrasions and sharp force injuries to the head, neck, torso and extremities.Senior Deputy District Attorney Jeffrey Dimmig said that the terms of the plea agreement were that Silvonek plead guilty to all charges and be sentenced to a life imprisonment and will be eligible for parole after 35 years.PlanningDimmig said Jamie Silvonek talked about planning her mother's death and said in one text message to Barnes, "I want her gone."Dimmig said the messages also indicate that the 14-year-old lied about her age to Barnes and told him she was 17.In October 2014, Jamie Silvonek, who was then 13, met Barnes, then 20, at a concert in Philadelphia. Silvonek told Barnes that she was 16 years old. During the subsequent months, they communicated daily via voice, text and social media and met on several occasions in Carbon County while Silvonek was visiting family there.Cheryl Silvonek met Barnes for the first time the morning of March 7, 2015, when she discovered her daughter with Barnes in the basement of her residence. When she learned that Barnes was 20 years old, she instructed her daughter and Barnes to end the relationship. Barnes returned to Fort Meade, Maryland, on March 7, 2015, where he was stationed in the Army.In a phone conversation that evening, Jamie Silvonek and Barnes discussed killing Silvonek's parents. The plan involved luring her parents away from the Silvonek house to a place where Barnes could kill them and then rejoin Jamie Silvonek to dispose of the bodies.On the morning of March 14, 2015, Barnes left Fort Meade for Jamie Silvonek's house. He had purchased tickets for a concert in Scranton that evening. Jamie Silvonek, an eighth-grade student, had taken a standardized test that morning.Text messagesAt 11:05 a.m., Cheryl Silvonek called Barnes on his cellphone. Text messages starting at 11:12 a.m. on March 14, 2015, show that Jamie Silvonek wanted Barnes to tell her mother that he was 16 ½ years old.Jamie Silvonek and Barnes also sent messages about telling the victim that someone else would be going to the concert with them.In text messages, Cheryl Silvonek appeared adamant. "He is not coming to this house," she texted.Jamie Silvonek texted Barnes: "She needs to go, Caleb. Right now. You don't understand."In a text message at 1:30 p.m., Jamie Silvonek texted, "She threatened to throw me out of the house. I want her gone." Sixteen minutes later, she texted Barnes, "I just need to you [sic] be able to come over so we can do whatever necessary, honestly."At 2:25 p.m. Cheryl Silvonek texted her husband, David Silvonek, who was at work, that their daughter's "friend" got tickets to a concert in Scranton and that she would be driving them. David Silvonek did not know about the relationship between his daughter and Barnes.A forensic review of the defendants' cellphones and the content of phone records provided text messages that had been deleted from both phones but were recovered.At 4:27 p.m., Jamie Silvonek wrote: "I'm going to go to the bathroom while you do it okay. I'll come right out as soon as you're done." At 4:42 p.m., she wrote, "Why don't we wait until we get in the car with her?"Barnes replies, "Fine."At 5:14 p.m., Jamie Silvonek wrote, "Just do it."At 5:56 p.m., E-ZPass records indicated, the Ford Freestyle entered the turnpike toll plaza going north toward Scranton. A minute later, Jamie and Barnes began texting each other while in the Silvonek vehicle. Jamie wrote, "I love you. We can do this…We'll just drive her car then, right?"Barnes replied in a text, "No. That leaves us as the suspects."After the concertVideo footage from the venue in Scranton showed the defendants entered the concert at the Hilton Hotel at 8:32 p.m. and leaving at 10:24 p.m.They later arrived in the driveway of their home at 1 a.m.Jamie Silvonek and Barnes were in the rear seats of the vehicle when Barnes, seated directly behind Cheryl Silvonek, began to choke and punch her from behind. According to police, the struggle lasted more than 20 minutes, during which time Cheryl Silvonek blew the vehicle's horn with her feet several times. Barnes then took out a knife and stabbed Cheryl Silvonek repeatedly in the neck.The defendants disposed of their clothing in the home and then left in Barnes' Chevrolet Camaro for the Walmart in Lower Macungie Township.They arrived at 2:08 a.m. and purchased various cleaning supplies, including bleach and wipes. The defendants left Walmart at 2:31 a.m. and returned to the residence, where they attempted to clean the inside of Cheryl Silvonek's vehicle.Police said Jamie Silvonek and Barnes took shovels from the garage and drove the Freestyle to Hassadahl Road. They buried Cheryl Silvonek in a shallow grave between the road and a nearby creek.A neighbor, alerted by the barking of his dogs, discovered the unoccupied Freestyle parked along Haasadahl Road and saw blood in the interior. He notified police who discovered a body, later identified as Cheryl Silvonek, buried in the loosely packed dirt and snow and then located the vehicle registered to David Silvonek.Police went to the Silvonek residence on Randi Lane where they found the defendants undressed and in bed together in an upstairs bedroom. David Silvonek also was in the house.