PITTSBURGH — The prosecution rested Thursday in the corruption trial of suspended Pennsylvania Supreme Court Justice Joan Orie Melvin and her suspended aide and sister, Janine Orie.

The defense will begin calling witnesses Friday to rebut claims by Allegheny County prosecutors that the sisters conspired to illegally use Melvin’s state-funded Superior Court office and staff to campaign for the state’s highest court in 2003 and 2009, and to use the state-funded staff and offices of a third sister, former state Sen. Jane Orie, for the same purposes.

A prosecution accountant has testified that the work of six staffers alone — four of Sen. Orie’s and two of Melvin’s — cheated taxpayers out of $33,000.

The sisters claim the work wasn’t illegal because Melvin’s staff completed their assigned work or it amounted to too little to be a crime.