Clearance Rates and Crime: Why Detective Work Doesn't Move the Needle

Introduction: Clearance Rates and the Role of Detectives

The FBI Uniform Crime Reports for 2001 indicated that the clearance rate for homicides was 65% (Richardson and Kosa 1). The clearance rates for other types of crimes — such as assault, theft, or rape — were all much lower than this. For the uninitiated, clearance rate refers to the rate at which police departments are able to gather sufficient evidence to charge and arrest an individual. Clearance rates are not the same as conviction rates, nor do they necessarily imply a one-to-one correlation with crime rates. Nonetheless, increasing clearance rates is generally perceived to be a good thing, primarily because it means that police are solving a greater number of crimes. Arrested suspects might not ultimately be convicted — for unrelated reasons — but offenders certainly face no danger of conviction if police cannot even clear their case in the first place. Thus, understanding the factors that can affect clearance rates in police departments is a crucial component of the police's role in maintaining order and punishing offenders for crimes.

With clearance rates as low as the figures cited by the FBI, it might seem surprising that police are able to clear any crimes at all. An examination of the way police work is actually conducted, however, reveals that very specific aspects of police work affect clearance rates. Surprisingly, changes in detective procedures or resources are not a significant factor. Within the bureaucracy of most police departments, detectives are the officers assigned with the task of clearing crimes perpetrated within their jurisdiction. According to popular media, detectives doggedly pursue suspects, amass hidden evidence, and make brilliant leaps of deduction in order to catch criminals. As a result of this image, the natural impulse when combating low clearance rates is to simply hire more detectives or change some aspect of detective work to make investigators more efficient. Unfortunately, detectives rarely behave like those we see on television or in the movies. Instead of being hired for Holmes-like reasoning abilities, detectives are more often promoted to become "consummate bureaucrats" whose primary task is to triage cases, read reports, complete paperwork, hold meetings, and discuss general policing procedure (O'Connor).

A survey of the available literature and research on the subject — particularly the oft-cited RAND Report from 1975 — reveals that no increases in the number of detectives or other changes in detective work will have an appreciable impact on the clearance rates of police departments. Similarly, clearance rates are not positively associated with crime rates, meaning that changes in detective work will not have a significant effect there either. Though common sense tells us that more police — in this case more detectives — will increase the effectiveness of police to clear cases and reduce crime, the evidence does not support this assumption. We must instead accept the reality that more detectives, or other changes to detective work, will not raise clearance rates or lower crime rates.

Clearance Rates and Crime Rates in the United States

Clearance rates in the United States, according to available statistics, are lower than the public, politicians, or even the police would like. The highest clearance rates are for murder cases, though the FBI reports that even the clearance rate for murder remains below 70% (Livingston). Some sources place the rate as low as 60% for homicides (Christianson). Unfortunately, these are the highest rates of case clearance reported anywhere in the system. When other types of crimes are considered, the rates of clearance drop significantly. In the mid-1990s, the clearance rate for robberies was an abysmal 25%, while the clearance rate for burglary or theft cases was even lower, at less than 20% (Livingston). By the start of the twenty-first century, clearance rates had plummeted even further, following trends that had been developing over the previous two decades.

Homicide clearance rates of approximately 60% today contrast sharply with clearance rates of 90% fifty years ago. Today, rape cases clear at a rate of 42%, robberies at 26%, and burglary at 13%. Between 1980 and 1996 alone, the national homicide clearance rate plummeted by 7% (Wellford and Cronin 3; Christianson). These falling rates suggest that insufficient resources are being allocated to solving crimes, or that the available resources are being seriously mismanaged.

The Relationship Between Clearance Rates and Crime Rates

What makes the situation even more confusing is that while crime rates nationally in the United States have been falling over the last decade, clearance rates are at their lowest levels ever (Christianson). The obvious implication of this statistical reality is that clearance rates do not necessarily exert a positive effect on crime rates. This is not to say they will have a negative effect, but if there were a one-to-one relationship between the two, we should expect to see crime rates rise when clearance rates fall. Because this is not borne out by the evidence, we can rightly assume that increasing the clearance rate will not decrease the crime rate. The conclusion is straightforward: manipulating clearance rates will not have an appreciable effect on crime rates.

This conclusion should be fairly obvious even without resorting to historical evidence. Clearance rates are indicators of how effectively police departments solve crimes that have already occurred. In order to raise clearance rates, it is necessary to solve more cases. Crime rates, however, are indicative of how much crime is being committed. In order to reduce crime rates, it is necessary to enact preventative measures that stop crime from occurring in the first place. Solving a preexisting crime will have no effect on crimes that are yet to occur — unless one argues that clearing an existing case prevents that particular criminal from reoffending. That, however, is a dubious assumption at best, and is entirely unsupported by the fact that clearance rates have been decreasing even as crime rates have declined as well.

The Role of Detectives in Clearing Cases

Having established that crime rates will not be appreciably affected by clearance rates, we are still left with the matter of diminishing clearance rates and what to do about them. If clearance rates are still falling, it means that criminals have an increasing chance of escaping detection entirely. In order to understand the factors that have been affecting clearance rates — and why more detectives will not improve the situation — we must consider the role detectives play in clearing cases, the relevant studies on this subject, and why cases end up being cleared at all.

The role of detectives within a police department is straightforward: investigate and clear crimes. To accomplish this, detectives are given general knowledge of the skills needed to solve cases, such as forensics or criminal profiling. In some larger police departments, detectives may be granted specialized training in one or two categories of crime to increase their effectiveness. They are armed with a basic knowledge of how to secure evidence and synthesize it in order to solve and clear cases (Purpura 167).

Unfortunately for the ego of detectives everywhere, the primary action detectives find themselves tasked with is not breaking down doors or deducing the whereabouts of a kidnapped victim, but rather filling out and processing paperwork. It has been estimated that nearly 80% of the crimes cleared in the average national police department are due entirely to the initial hard work of patrol officers who compile evidence and gather witness statements. Credit is given to detectives for solving these crimes when they synthesize that information into a single file and make an arrest (O'Connor). In general, cases are not cleared because detectives are especially brilliant, effectively trained, or sufficiently numerous, but rather because witnesses were available at the scene to tell detectives who committed the crime (Livingston). This conclusion might seem unpalatable to those raised on police dramas, and may sound downright insulting to actual detectives, but it is nonetheless supported by numerous studies on the subject.

Conclusion: What Actually Affects Clearance Rates

The conclusions we can draw from this data are clear: putting more police detectives on the job or changing police procedures related to detectives will not have an appreciable effect on clearance rates or crime rates. We have established that crime rates and clearance rates are not positively associated, despite common-sense notions to the contrary. Clearance rates, moreover, cannot be improved simply by increasing detective staffing or altering detective procedures. Instead, numerous studies — including the pivotal RAND study of the 1970s — conclude that the most important factors related to case clearance are response time and the availability of useful witness information at the scene. Since neither of these factors can be directly affected by changes in the number or kind of detectives, we can conclude that such changes will not be meaningful in improving case clearance rates or reducing crime rates overall.