From the Document: "President George W. Bush signed the Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act of 2001 ('USA PATRIOT Act' or Act) on October 26, 2001. Section 213 [hyperlink] of the Act, enacted as part of the legislative response to the September 11, 2001, terrorist attacks, authorizes sneak and peek search warrants. 'Sneak and peek' refers to the unannounced execution of a warrant on premises where officers observe, examine, measure, conduct tests, and otherwise surreptitiously search, but do not seize tangible property, and where officers thereafter delay notice of the search for 30 days. Notice permits an individual to challenge the legality of the search. It could also lead to flight, destruction of evidence, or placing a witness in peril. In FY2020, under the authority of Section 213, courts issued close to 20,000 such 30-day, delayed-notice search warrants, and approved extended delayed notice beyond 30 days in more than 10,000 cases. Drug cases accounted for more than 70% of the total number of the delayed-notice warrants issued. Authorities used delayed-notice warrants in fewer than 250 terrorism investigations."
CRS Legal Sidebar, LSB10652
Congressional Research Service: https://crsreports.congress.gov/