“After seeing the video evidence, prosecutors dropped all charges against Jones. The police department eventually launched an investigation that resulted in Antkowiak resigning.”
Right there. Ridiculously slow followup but the DA’s office in screening. None by the PD until -finally- some assistant district attorney caught it. FYI in a major city ADA’s can easily put in 80 - 90 hour work weeks if they strive to carry out all their obligations. The flow of cases and data is like trying to drink from a fire hydrant.
Resigning?
The guy spent 15 months in jail. A resignation is clearly not sufficient.