Teresa Youngblut had foil-wrapped phones & tactical gear in car in immigration stop shooting
Why Does Foil Block Wireless Signals?
Wireless signals are ultimately just radio waves, which are a type of electromagnetic wave. Metals, like aluminum foil, are electrically conductive, and can block or reflect radio waves that come into contact with them.
So, if you surround something that can transmit or receive wireless signals with aluminum, itโll block any wireless signals.
https://www.howtogeek.com/heres-what-wrapping-your-phone-in-aluminum-foil-does/