In the US, a no knock warrant is a warrant issued by a judge that allows law enforcement officers to enter a property without immediate prior notification of the residents, such as by knocking or ringing a doorbell. In most cases, law enforcement will identify themselves just before they forcefully enter the property. It is issued under the belief that any evidence they hope to find can be destroyed during the time that police identify themselves and the time they secure the area, or in the event where there is a large perceived threat to officer safety during the execution of the warrant. The Department of Justice writes: "Federal judges and magistrates may lawfully and constitutionally issue "no-knock" warrants where circumstances justify a no-knock entry, and federal law enforcement officers may lawfully apply for such warrants under such circumstances. Although officers need not take affirmative steps to make an independent re-verification of the circumstances already recognized by a magistrate in issuing a no-knock warrant, such a warrant does not entitle officers to disregard reliable information clearly negating the existence of exigent circumstances when they actually receive such information before execution of the warrant". The number of no-knock raids has increased from 3,000 in 1981 to more than 50,000 in 2005, according to Peter Kraska, a criminologist at Eastern Kentucky University in Richmond, Kentucky. Raids that lead to deaths of innocent people are increasingly common; since the early 1980s, 40 bystanders have been killed, according to the Cato Institute in Washington, DC