Police officers really have no choice but to open carry. Anyone remember the 1960s and early 70s? Black Liberation Army? At the time, NYPD carried their wheel guns in open top leather Jay Pee holsters, exposed to the elements. The holster came apart during a gun grab and felons refined and practiced their disarming techniques while in prison. Two sets of NYPD officers murdered were Foster and Laurie, then Jones and Piagentini. There were others.
This is the era that led to retention holsters, enhanced materials, steel reinforcement and handgun retention exercises and training. At the time, I knew several officers who carried their wheel guns with empty shell casings in them and a Browning Hi-Power concealed in a shoulder holster. The Hi-Power was the only high capacity auto available.
If young, uniformed police officers working high crime areas can be successfully disarmed, the open carry CCW will fare no better. Incidentally, one major reason for not carrying cross-draw is that the butt and grip face your adversary during a confrontation.
Int'l Assoc. of Law Enforcement Firearms Instructors