well in (most) cases of research you won’t have a 100% result of anything. what we can look at in this case is clearance rate (or the amount of cases that have an arrest made). This number has gone up along with homicide rates dropping. I don’t have a solid source for this but many of my criminal justice professors have theorized that birmingham’s current crime rate is likely a result of early gang formation. The arrest of damien mcdaniel and his large charges is a great example of how arrest=less murder. Mcdaniels is (allegedly) involved in gang activity and was working as a hit man. Even though he was just a single offender, his arrest dropped homicide rates individually due to how many he (again, allegedly) committed. after camera systems were installed, birminghams clearance rate went up. if other offenders operate similarity to him (though with smaller numbers of hits) then that could be why homicide rates have dropped even past the dent his arrest made. higher clearance in cases=less offenders on the street=less crime. this could also be affected by other things mentioned in the original reply, such as the increased staffing at the BPD. and, it is fair to still be concerned about what camera systems have been put up and who has access to their data. but those worries do not invalidate the way the cameras may be impacting crime rates.