Joan Orie Melvin, 56, was convicted of theft of services, conspiracy and five other charges, The Wall Street Journal reported. Her sister, Janine Orie, 59, who worked in her office, was found guilty of six counts.
The jury in Allegheny County had been deliberating since Friday. They were unable to reach a verdict on an official suppression charge that involved the dismissal of a law clerk in 2003, allegedly because she did not want to do political chores.
Another sister, former state Sen. Jane Orie, was found guilty last year of using her own official staff in Melvin's campaign and sentenced to up to 10 years.
Melvin, a Republican, ran for the state Supreme Court in 2009 and won a 10-year term after losing in a bid for the court in 2003. She was suspended last year after she was formally charged.