The Fourth Amendment obliges the government to demonstrate probable cause before conducting invasive surveillance.
Traditionally, prosecutors may ask judges to wiretap lawyer-client conversations if they can demonstrate probable cause that the lawyer is being used to carry out a criminal enterprise.
The F.B.I. does not need to demonstrate probable cause that a crime has been committed, or any connection to terrorism.
WASHINGTON, Sept. 26 — A federal judge in Oregon ruled Wednesday that crucial parts of the USA Patriot Act were not constitutional because they allowed federal surveillance and searches of Americans without demonstrating probable cause.
Some blame this on a change to the extradition law in 2003: whereas Britain must demonstrate "probable cause" before a suspect may be extradited from the United States, America need prove only "reasonable suspicion" before Britain will hand a suspect over.
The warrant requirement ensures that officials demonstrate "probable cause" to an independent judge before conducting a search, in a process that mandates a specific description of the information they're seeking.
An ACLU records request of 250 police departments nationwide found that "virtually all" respondents said they track cell phone location data maintained by cellular companies, and "only a tiny minority reported consistently obtaining a warrant and demonstrating probable cause to do so".
