Yes. Once bail is set, you can get it reduced. You can either petition the judge who originally set your bail, ask for a reduction at your preliminary hearing, or file a motion with the miscellaneous criminal court judge in the Court of Common Pleas in the county in which the case is listed.
The real question however, is, "will the bail get reduced?"
There are two separate arguments I make for bail reductions when advising my clients. These arguments are simply my opinion and not necessarily driven by any specific law, but they give my clients an idea of whether they actually have a shot to get the bail reduction.
Three factors go to the bail number itself. First, the seriousness of the current offense. Someone arrested for stealing a car should not have as high a bail as someone who is arrested for rape. Second, the defendants prior record of convictions. If one person has ten conviction versus another person who has no prior convictions, this is a huge factor for bail. Third, the likelihood the defendant will appear in court. Do they have previous bench warrants, where do they live, do they have ties to the local community?
The second issue at a bail reduction is whether there is a change in circumstance. The three prongs I mentioned in the previous paragraph are important to set the bail, but what happens if the charges are rape and the "victim" fails to appear for the preliminary hearing at the first two listings and the judge continues the preliminary hearing for a third time? What if there is no rape kit and no dna collection too? In that instance, I would argue that there is a change in circumstance: the complainant does want to prosecute and commonwealth has no case. At the time the bail was set, the court thought this was going to be a "real" rape prosecution, now this is just a way to get my poor client locked-up for several months with no recourse. Accordingly, the bail should be reduced.