Prosecutors in Allegheny County allege that 60-year-old Gloria Mazzocco of Imperial loaned her son two guns used in the March 11 shootings at the Fort Pitt Inn.
She is charged with conspiracy and two firearms charges; a third weapons count was dropped. A judge ruled Monday that there was enough evidence to take the case to trial.
Twenty-five-year-old David Mazzocco is charged with killing 29-year-old James Adams of Imperial and wounding two other men.
Prosecutors have said he was barred from owning firearms but his mother told investigators that she gave him the guns to show to someone interested in purchasing them.