"Parallel reconstruction" is when law enforcement uses secret surveillance techniques to try to find evidence. Then they try to seek it out again making it look like they didn't violate rights by being intentionally vague about where they got their evidence, suggesting it wasn't so nefarious. Devices like Stingrays are often used by law enforcement in "parallel reconstruction." Stingrays are devices that behave like fake cellphone towers, tricking phones into believing they're pinging genuine towers nearby. By using the device, cops can determine a suspect's precise location, outgoing and incoming calls, and even listen in on a call or see the content of a text message. Real cell phone towers just aren't that accurate. And all of this is being done without consent or the knowledge of most of the American civilians.
Hemisphere, a massive telephone-call gathering operation revealed by The New York Times in 2013, is one of the most well-documented surveillance programs that government officials attempt to hide when they use parallel construction. The largely secret program provides police with access to a vast database containing call records going back to 1987. Billions of calls are added daily.