Incidental collection happens when an individual is in contact with the target of surveillance. So if Bob were being targeted for surveillance and Alice called or emailed Bob, Alice’s communications with him would be collected incidentally. Incidental collection happens over the course of most surveillance, whether it is targeted surveillance under traditional FISA authorities, or it is large scale surveillance pursuant to Section 702 of the FISA Amendments Act where vast amounts of Americans’ communications are swept up by the National Security Agency (NSA).

Under traditional FISA authorities, surveillance is targeted at a single person, and the NSA conducts it pursuant to a warrant based on probable cause that the target is a foreign power or an agent of a foreign power. Here, if Bob is targeted for surveillance and Alice contacts him during that surveillance, resulting in the incidental collection of her communications with him, her name should be redacted or “masked” unless leaving it un-redacted provides foreign intelligence value.

But, there’s a loophole. If the NSA analyst reviewing the information believes Alice’s communications may contain evidence of any crime, the NSA can share those communications with law enforcement or other relevant agencies. Those agencies can use that information in their investigations and prosecutions, even if the crimes are completely unrelated to the purpose for surveilling Bob’s communications, or to foreign intelligence or national security investigations.