Attorneys for a teenager convicted in the murder of her mother in eastern Pennsylvania four years ago are seeking a new trial, calling the outcome of her case "shocking."

Now-18-year-old Jamie Silvonek was sentenced to 35 years to life after pleading guilty in the Lehigh County killing of 54-year-old Cheryl Silvonek in 2015, when the teen was 14. Co-defendant Caleb Barnes of El Paso, Texas, a soldier at Fort Meade, Maryland, was convicted of first-degree murder and sentenced to life without parole.

Authorities said Barnes stabbed the victim in her car after Barnes, Cheryl Silvonek and Jamie Silvonek returned home from a concert. Prosecutors said the woman had threatened to report Barnes, then 21, to police for having sex with her underage daughter.

Silvonek testified at Barnes' trial that she plotted the murder and urged her boyfriend, in a series of texts, to carry it out. Jurors rejected Barnes' argument at trial that the girl killed her mother and he only helped dispose of the body later because she said she was pregnant.

Silvonek's new attorneys argue that not enough evidence was presented by her previous defense about her background and mental health, leading to what they called "an inaccurate, myopic view of Jamie as lying, manipulative and savvy beyond her years," The (Allentown) Morning Call reported.

Her previous attorney, John Waldron, defended his representation Tuesday and said he "wouldn't have done anything differently." He said he called three expert witnesses seeking to have her tried as a juvenile, but once the judge ruled against that his options were limited. Prosecutors wouldn't drop the first-degree murder charge and the judge warned that she wouldn't accept a plea deal for a sentence less than 35 years, he said.

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Information from: The Morning Call, http://www.mcall.com