The ruling came Tuesday in the case of Keith Garner.
Also charged with homicide in the case are Jahlil Porter and Robert Long, who waived their preliminary hearings.
A fourth man originally charged in the slayings now faces only drug and conspiracy counts.
Investigation continues into quadruple killing in Southwest Philadelphia
Authorities said two stepbrothers, 31-year-old William Taylor and 28-year-old Akeem Mattox, found the drugs while renovating homes.
They say an attempt to sell the drugs in November 2018 led to their deaths and those of two sisters, 20-year-old Tiyaniah Hopkins and 17-year-old Yaleah Hall.
Garner's attorney, Coley Reynolds, tried to poke holes in the testimony of witnesses during the hearing.