A clearance rate refers to the number of cases that are solved by a particular law enforcement agency. It is one measure of an agency's skill and efficiency in solving crimes, but it is often used in conjunction with many other benchmarks if used at all. The clearance rate may be divided up in a number of different ways, including the type of crime being committed, or the seriousness of the crime. Clearance rates are not linked to convictions.
Law enforcement agencies clear a crime in one of two ways. The first way is when an arrest is made. This scenario is how most cases are cleared, and how the clearance rate is typically impacted. The other way a case can be cleared is when a situation makes it impossible for police to arrest the perpetrator. This occurs in cases where the suspect has died, or where the victim may not be cooperative in the investigation and refuses to press charges.
The clearance rate may not be strictly defined from one agency to another. Some agencies may define a clearance rate simply as when an arrest is made. Some may define it simply as identifying a suspect, whether or not that suspect is actually taken in to custody. An acquittal on a charge does not mean the case is not considered cleared from a law enforcement perspective.
Further, the definition of a crime may also change from one jurisdiction to another. Some jurisdictions may have laws that are more strict than another jurisdiction, and those laws may be harder or easier to enforce. Also, police investigators may not officially classify an incident as a crime in order to positively affect clearance rates. This makes comparing data, or even relying on any portion of the data, extremely questionable.
Generally speaking, the clearance rates for serious crimes, especially crimes against individuals, are higher than those rates for less serious crimes. This may provide an indication of how limited resources in a law enforcement agency are spent. For example, a 2009 study in the state of Nevada that analyzed 10 years of data found that the clearance rate for murder was 80%, but the rate for motor vehicle theft was only 7%.
In the United States, the national clearance rates for more serious crimes such as murder, rape, robbery, and aggravated assault stood at 22% in 2009. That number included a total of approximately 9.4 million cases investigated by local, state, and federal agencies. The long-term national trend for the rate in the United States is more than 20%.