[3] From 1993 until his confirmation, Mariani was a lawyer in sole private practice in Scranton, specializing in labor and employment law.

[4] Mariani spent the majority of his career representing unions and employees in labor and employment matters.

[7] On December 1, 2010, President Barack Obama nominated Mariani to a vacant judicial seat on the United States District Court for the Middle District of Pennsylvania that previously had been held by Judge James Martin Munley, who assumed senior status in January 2009.

The American Bar Association rated Mariani Unanimously Qualified for the nomination.

He assumed senior status on September 30, 2022,[2] but maintains an active docket.