PITTSBURGH — The words of former state Supreme Court Justice Joan Orie Melvin are being used by a prosecutor who’s trying to block an appeal of the public corruption conviction and prison term handed to Melvin’s sister.

Melvin, 57, is serving three years of house arrest after her February conviction in a related campaign scandal prosecuted by the office of Allegheny County District Attorney Stephen Zappala. His quoting of her in the case of her sister, former state Sen. Jane Orie, is the latest salvo in a war of words waged since Zappala began investigating the sisters in late 2009.

“The Court’s only armor is the cloak of public trust. Its sole ammunition is the collective hope of our society,” Zappala quoted Melvin as saying when she was sworn in as justice in January 2010. A footnote shows the quote was taken from video posted on a newspaper website.

Wednesday’s filing comes in response to the Superior Court appeal of the former justice’s sister, Jane Orie. She is appealing her conviction last year of using state-paid staff to work on her own political campaigns and of introducing forged documents meant to discredit a key trial witness. The forged documents prompted Allegheny County Judge Jeffrey Manning to declare a mistrial in 2011.

Orie, 51, was sentenced to 2½ to 10 years in prison after a second trial in 2012. She has raised a dozen issues in her appeal, including that Manning was wrong to declare the mistrial, and the second trial amounted to double jeopardy — or unconstitutionally prosecuting someone for the same crimes twice.

Orie’s attorney, William Costopoulos, has argued prosecutors brought the forged documents to the judge’s attention only because they feared the jury deliberating in 2011 was about to acquit Orie. “The Commonwealth intentionally and deliberately provoked a mistrial in this case,” Costopoulos wrote in his April appeal brief.