While many states in the US have laws prohibiting the use of mobile phones while driving, Florida isn’t one of them.
The Tampa Tribune reports that Mr Humphreys took it upon himself to ensure any fellow motorists driving within range of his signal-jamming device would be unable to make or receive calls.
The vigilante could still have been in the act of enforcing his own anti-mobile-phone law, if not for a wary phone service provider who noticed a peculiar signal outage on one of Florida’s main roads.
The US Federal Communications Commission investigated, and found the source of the signal outage was coming directly from Mr Humphreys’ Toyota Highlander (Toyota Kluger in Australia).
Florida police finally stopped the car around a year later, and immediately knew they had found their man when their radios lost contact with their home base.
After finding the device hidden behind a seat cover, police have now served the 60 year-old man with around US$48,000 (AU$51,797) in fines, for which he has 60 days to either respond to or pay them.
US federal law prohibits the use, importation, marketing, sale or possession of mobile phone jamming devices outside of law enforcement, primarily to ensure emergency calls are unlikely to be blocked.