While the idea that the mere presence of police in a community cannot deter crime from occurring may be a bit saddening or hard to believe for many, the truth is simply that the Kansas City Preventive Patrol Experiment showed that it couldn't. While patrol may be considered the "backbone" of police work, as it has long been, the theory had not been scientifically tested until 1972 in Kansas.
One of the most significant findings of the experiment was that people -- citizens -- did not realize when there was a difference in the level of patrol deployed. Another finding, there was no change in the number of burglaries, auto thefts or vandalism when there were more or less police patrolling. These crimes were always considered "preventable" -- if only there were more police preventive patrolling going on in the community. The study proved that this just wasn't so.
While the findings could always be debated, there is a lot of work here that shows that funds may be more wisely allocated to another strategy rather than preventive patrolling when it comes to actually preventing crimes. Perhaps in another city, deploying vast amounts of preventive policing may work, but it is highly likely that any other cities would find the exact same results.
The study showed that preventive policing was ineffective when it came to preventing burglaries, robberies, auto theft, vandalism -- and other types of crimes; there is little evidence to believe that other types of crimes may be more or less prevented based on the experiment. Domestic violence, which normally takes place at a home residence, may not be affected by preventive policing, just as child abuse may not. However, crimes like prostitution or drug dealing may be prevented as the more visible police there are on the streets, the fewer places these people have to go to do what they need to do. Therefore, it seems obvious to state that preventative patrolling would be most effective with crimes such as prostitution and drug and arms dealing; however, vandalism is a crime that would seem to be preventable with random preventive policing, so it is hard to tell.
The reason that preventive policing is not effective mainly comes down to the fact that in order to prevent something, the prediction of where that something is going to occur must have taken place, and this is nearly an impossible feat.
It depends on a theory of causality, and when applied to social constructs such as crime and criminality it is very uncertain, drawing as it does upon social scientific knowledge and understanding that has historically proved to be 'more successful at predicting the experience of populations than of individuals (Freeman 1992:36; Gilling 1997:2).
While preventative patrol policing may work some of the time, it cannot be established as an efficient way of preventing crime as studies have shown that it does not deter crime, nor does it make citizens feel safer. The main arguments against preventive patrol policing are that 1) even though police are able to cover more area, there are never able to predict where crime happens and thus it makes it so that any crime they do come across is completely random (this leads into the argument that police could be doing more efficacious duties with their time as opposed to waiting for happenstance to occur); 2) preventive patrol policing significantly decreases the face time that police have with actual citizens (this is probably the reason that most people do not feel safer when there is preventive patrolling going on in their community). In order for citizens to feel safe, they need face time with law enforcement. To simply see police officers driving around in cars won't do anything to boost their confidence; if anything, it makes police look like some kind of "big brother" checking up on them as opposed to fighting crime and keeping them safe.
Some people have compared preventive policing to preventive firefighting. Why would you have a bunch of firemen driving around looking for fires? It would waste resources and time. The same is relevant for police officers. They should save their time and resources for real crimes as opposed to seeking them out -- as the Kansas City Preventive Patrol Experiment proved that preventive patrolling was ineffective anyway.
Caro, Francis G. (1976). Readings in evaluation research. Russell Sage Foundation; 2nd edition.