When Hailey looks into the box of shoes she sees the ones that have blood on them, these have white soles, the photo of the shoes the detective puts up on the board have black soles.
After the DA is arrested, the jail cell she is in has lights with external cabling. No jail cell would use these since they could be ripped open by inmates. It's also rather large for a cell and has its own table and chair. This reveals it was a poorly constructed film set.
A district attorney being charged would not be prosecuted by her own office. The Governor would assign another prosecutor from outside the area.