Private donors including big-box stores, fossil fuel companies, and tech giants are secretly giving hundreds of millions of dollars annually to law enforcement agencies and related foundations, allowing police to buy specialized weapons and technology with little public oversight.

Experts say this huge deluge of police “dark money” funding, detailed in a new University of Chicago working paper and in an additional analysis shared exclusively with the Lever, leaves law enforcement beholden to the companies and powerful donors bankrolling them, rather than the communities that officers are sworn to serve.

“The big-picture finding is that the world of private donations to police is a lot bigger and more complex than previously estimated,” said Robert Vargas, a professor of sociology at the University of Chicago and a coauthor of the study.