Jurors said they were unable to reach a decision on one count: a charge of official oppression against Melvin, who was accused of firing her law clerk when she objected to doing political work in 2003.
The sisters were found guilty of theft of services and criminal conspiracy.
They were charged with conspiring to use Melvin's state-funded judicial staff
-- and the state-funded staff of a third sister, former state Sen. Jane Orie -- to campaign for the Supreme Court when Melvin was a Superior Court judge in 2003 and 2009.
The defense had claimed the charges were overblown or outright lies, while prosecutors charged that the sisters' family ties became "criminal ties" when they worked together to misuse the staffers and other state resources.
Melvin and Janine Orie have been suspended without pay and the Judicial Conduct Board has disciplinary charges pending against Melvin.
Although Jane Orie was charged as part of the conspiracy, she wasn't on trial. She resigned from office last year and is serving two and a half to 10 years in prison for her conviction on illegally using her staff to work on her own campaigns, though she was acquitted of charges that she had those staffers campaign for Melvin, too.
The sisters, both staunch Republicans, have long argued the prosecutions were the result of a political vendetta by Democratic Allegheny County District Attorney Stephen Zappala Jr., allegedly because the Ories have opposed the expansion of legalized gambling, an industry in which Zappala's relatives have an interest.
Zappala has repeatedly denied any improper
motive. He said the investigation began simply because an intern for then-Sen. Orie came to his office in October 2009 and complained about political campaign work that the lawmaker's staff was being made to do for Melvin, just days before she won a seat on the state's highest court.