The Patriot Act facilitates a number of processes that make it possible for law enforcement to investigate and prosecute terrorists. Many of the tools laid out in the Patriot Act had been employed against organized crime but were not available for use as instruments against terrorism, according to the Department of Justice.
The Department of Justice explains that the Patriot Act's contribution to the war on terror was not the creation of new mechanisms for bringing down offenders, but it was allowing law enforcement to use existing practices in new situations. For example, the Patriot Act allows the use of a roving wiretap for terror suspects. The roving wiretap--an authorization from a federal judge to freely tap all of a suspects' communications devices without the need of particular warrant for each device--had long been used against the mafia and drug traffickers. The Patriot Act makes it possible for law enforcement to obtain a roving wire tap order for suspected terrorists.
According to the Justice Department, the Patriot Act makes it possible for law enforcement officers to obtain warrants with limited delay notification. This procedure allows investigators to conduct an investigation without having to immediately notify terror suspects that they are being investigated. The measure is meant to preempt typical actions by criminals who know they are being investigated, such as destroying evidence or killing witnesses.
The U.S. Treasury's Financial Crimes Enforcement Network states that the Patriot Act lets investigators search bank and business records in order to detect terrorist funding and the purchase of destructive materials.