From the early 1800s to the 1980s, patrol and criminal investigation dominated policing. Uniformed police patrolled the streets to prevent crime, to interrupt crimes in progress, and to apprehend criminals. Whatever crimes patrol officers did not prevent, detectives attempted to solve by questioning suspects, victims, and witnesses. Research since the 1960s has shown the limits of both patrol and investigation for controlling crime. In the 1990s, the police adopted proactive policing strategies in which police initiate action instead of waiting for calls.
Patrol remains the backbone of police operations. It consumes most of the resources of police agencies. On patrol, a police officer makes regular circuits or passes through a specific area called a beat. Officers sometimes patrol on foot but usually ride in cars. The main advantage of car patrol over foot patrol is increased efficiency of coverage. A disadvantage of car patrol is that it reduces police contacts with citizens. Studies of foot patrol indicate that these patrols are costly and do not reduce crime. They do, however, make citizens less fearful of crime and improve citizen attitudes toward the police.
Patrol has three parts: answering calls, maintaining a police presence to deter crime, and probing suspicious circumstances. Of these, the second, preventive patrol, is the most controversial. A presumed advantage of patrol is that police cars cruising randomly through city streets supposedly create the feeling that the police are everywhere.
The Kansas City Preventive Patrol Experiment
Does random patrol in marked police cars really deter would‐be criminals from breaking the law? Does it actually make law‐abiding people feel safe? Does increasing the number of police reduce crime rates? In a controlled experiment done in Kansas City, Missouri, during the 1970s, researchers divided a 15‐beat area into three sections. In one area, the “reactive area,” police withdrew all preventive patrol and entered only upon citizen requests for assistance. In another section, the “proactive area,” police raised patrol to four times the normal level. The third section, in which the police maintained the usual level of patrol, served as a control.
The three areas were essentially alike, except that the citizens and criminals in two groups were exposed to preventive patrol, and the citizens and criminals in the other area were not exposed to preventive patrol. If the researchers had found crime rates to be significantly lower in the two areas with higher levels of patrol, they could have concluded that patrol does indeed cause crime rates to drop. Results showed that level of patrol had little effect on crime rates. Additionally, level of patrol had little influence on citizens' fear of crime or their satisfaction with the police.
Interpreting the Kansas City study
Carl Klockars, a University of Delaware professor, says, “It makes about as much sense to have police patrol routinely in cars to fight crime as it does to have firemen patrol routinely in fire trucks to fight fire.” Echoing this sentiment, many police departments in the United States shifted their focus from law enforcement to maintaining the order and serving the public. James Wilson interpreted the results differently. He argues that the Kansas City study shows only that random patrol is of questionable value. He points out that other types of patrol, such as foot patrols or patrols in unmarked cars, might reduce crime. Most observers agree on one thing: Simply increasing the number of police doesn't reduce crime. There is a consensus among experts that the number of police is not as important as what the police are doing.
While the mere presence of police in an area may not deter crime, aggressive patrol may make a difference. Proactive police operations focus on the concentration of crime in certain offenders, places, and victims. Proactive operations include using decoys, going undercover, raiding, relying on informants, stopping and frisking suspects, shadowing repeat offenders, policing repeat‐complaint locations, and saturating an area with police to maintain order.
Because crime is not evenly distributed throughout a community, it stands to reason that some places need more patrol than others. The tradition of giving each neighborhood an equal amount of patrol wastes police resources. A smarter use of resources would concentrate patrol on high‐crime times and places. The Minneapolis 911 study, for example, centered around hot spots. This study discovered that a small number of locations in Minneapolis accounted for a disproportionate number of the calls for police service. Brief periods of intensive patrolling reduced or displaced robberies and other offenses in high‐crime areas.
In another proactive strategy, aggressive field interrogation, the police check out suspicious persons and places. In the San Diego Field Interrogation Study, officers frequently stopped and asked people what they were doing. This strategy led to large drops in robbery, burglary, theft, auto theft, assault, sex crimes, malicious mischief, and disturbances.
In undercover police operations, still another proactive strategy, the police use covert means to identify criminal activity while it is happening. In New York City, the Street Crimes Unit (SCU) of the New York Police Department employs undercover officers to apprehend muggers. Officers disguised as potential victims walk the streets. When a mugger attacks one of these decoys, plainclothes surveillance officers who are dressed to blend in to the area intervene and arrest the mugger.
The TV image of detectives is that they sleuth out clues to solve most crimes. In the real world, however, police clear only 21 percent of all reported index crimes. Moreover, research suggests that detective work is boring and requires a good deal of paperwork. Finally, studies show that investigations seldom solve crimes because most crimes betray scant leads.
What do detectives do? If a crime has been committed but the police haven't identified or apprehended the suspect, detectives gather information that permits the identification and arrest of the perpetrator of the crime. On some occasions, detectives assume false identities, or “go undercover.” Undercover work can be useful in getting information on future criminal activity. Four important steps a detective takes to solve a crime are interviewing victims and witnesses, surveying the crime scene, collecting physical evidence, and using informants.
Several studies raise questions about the value of investigations in apprehending offenders. The National Institute of Justice (NIJ) sponsored studies that show that no amount of investigation will solve many serious crimes. The Rand Corporation study of investigators found that most crimes are cleared by patrol officers making arrests at crime scenes.
In big cities, special units deal with specific types of crime. The most common of such units are for traffic and drugs. Departmental policies guide traffic enforcement. Some departments expect officers to write a certain number of tickets each day. Similarly, some departments operate drunk‐driver checkpoints and other programs to target intoxicated people who operate motor vehicles. Departmental policies also dictate drug enforcement.
Most big‐city police departments have a special unit for enforcing drug laws. Officers working in these units engage in police crackdowns. The aim of crackdowns is to sharply increase police activity to get the largest number of drug arrests and to stop street dealing. Officers employ undercover and buy‐and‐bust operations (in which officers pretend to be buyers). Police also use sweeps (in which the police arrest all those suspected of drug‐related crimes), raids on apartments and other dwellings (in which officers rely on no‐knock search warrants to attack drug dealing as it moves inside from the streets), asset forfeiture, and reverse stings (in which officers pose as sellers instead of buyers). Police crackdowns on drugs have produced mixed results. It is unclear whether these operations shift the drug market to other areas or actually reduce the availability of drugs.