so in my opinion i think either the spy cam methods or the hard methods to deter the bugger would be a better idea. I too agree, reporting to police is not much of a help, the pervert might time the routine patrols and strike at his own convienience.
to add another suggestion, spend some money, hire a private investigator, stake out at opposite block or something. Take photos of the pervert for evidence. Nail that bugger once and for all. =D