Police let most Capitol rioters walk away. But cellphone data and videos could now lead to more arrests.

Authorities looking to prosecute the mob of Trump supporters who overran the U.S. Capitol on Wednesday stand to get powerful help from cellphone records, facial recognition tools and other technologies to assist in the identification of anyone who was there that day.

The Capitol, more than most buildings, has a vast cellular and wireless data infrastructure of its own to make communications efficient in a building made largely of stone and that extends deep underground and has pockets of shielded areas. Such infrastructure, such as individual cell towers, can turn any connected phone into its own tracking device.