FBI has acknowledged that the law enforcement agency uses drone aircraft in the United States for surveillance in certain cases.
The information was shared by the FBI in a letter to Senator Rand Paul, who released the unclassified version of the letter on Thursday.
Noting that it uses drones in very limited circumstances to conduct surveillance when there is a specific, operational need, the FBI said these have been used for surveillance to support missions related to kidnappings, search and rescue operations, drug interdictions, and fugitive investigations.
"Since late 2006, the FBI has conducted surveillance using unmanned aerial vehicles (UAVs) in eight criminal cases and two national security cases," the FBI said.
For example, earlier this year in Alabama, the FBI used UAV surveillance to support the successful rescue of the 5-year-old child who was being held hostage in an underground bunker.
None of the UAVs used by the FBI are armed with either lethal or non-lethal weapons, and the FBI has no plans to use weapons with UAVs, it said.
The FBI does not use UAVs to conduct "bulk" surveillance or to conduct general surveillance not related to an investigation or assessment, the federal agency said.
In a follow-up letter, Paul sought details from FBI on its interpretation of a "reasonable expectation of privacy" that would trigger the warrant requirement.
"I ask that you provide me the Bureau's definition of when an individual has a reasonable expectation of privacy," he wrote.