Convicted murderer Jeff Pelley is requesting a new trial.
Last month, he was sentenced to 160 years in prison for the 1989 murders of four family members.
Now 34, he apparently killed his father, stepmother and two stepsisters in their Lakeville home, so he could attend his high school prom.
According to Pelley's attorneys, a woman claims she overheard a group of teens talk about killing one of the victims two weeks before the murders.
The witness surfaced after Pelley's July conviction. Prosecutors say they never heard of the woman.