Jacob Sullivan pleaded guilty to first-degree murder and related charges in the 2016 slaying of Grace Packer. Jurors spent hours in the deliberating room before telling a judge on Wednesday they are deadlocked on the sentence. They were ordered to keep at it.
Talks will resume Thursday.
Death penalty sought for man charged in Grace Packer killing
If the jury can't come to a unanimous decision, Sullivan will automatically get life without parole.
Grace's mother, Sara Packer, is due to plead guilty for her role in the gruesome plot. In a plea deal with prosecutors, she'll be sentenced to life without parole.
Prosecutors say Sullivan acted out a rape-murder fantasy he shared with Sara Packer.