As the search intensifies for missing 84-year-old Nancy Guthrie, investigators are turning to an unlikely tool — a custom-built Bluetooth “signal sniffer” designed by a former Marine and cybersecurity expert.
David Kennedy, CEO of cybersecurity firm TrustedSec and a veteran who conducted cyber missions for the National Security Agency, said he developed the technology specifically to aid in the search after learning that Guthrie had a newer-model pacemaker equipped with Bluetooth connectivity.
“When this whole Nancy Guthrie case came out, law enforcement said that her pacemaker had disconnected from her phone,” Kennedy explained. “That would indicate she’s using one of the newer brand pacemakers that have Bluetooth connectivity.”
Kennedy, who previously worked with pacemaker manufacturers to test devices against cyber vulnerabilities, said he quickly recognized an opportunity to help. Drawing on his experience with Bluetooth low-energy (BLE) systems, he wrote software capable of scanning for specific Bluetooth signatures — even those designed to obscure a device’s identity.
The system, now attached to a Pima County Sheriff’s Department helicopter circling Tucson, Arizona, uses high-gain antennas, signal amplifiers, and software-defined radios to extend detection capabilities. While Bluetooth low-energy devices typically transmit within a 30- to 35-foot radius, Kennedy’s setup can detect signals up to 800 feet away under current operating conditions.
“In a perfect world, with no obstructions and clear line of sight, it could go much farther,” he said — potentially up to 5,000 feet. But real-world obstacles, including walls and even the human body itself, significantly reduce effective range.
The technology works by broadcasting energy outward in a large radius, attempting to intersect with the pacemaker’s limited signal bubble. If the sniffer gets close enough, it can perform “active scanning,” attempting to communicate with the device and confirm its identity.
Critically, because Guthrie’s pacemaker was paired with her phone, it may periodically attempt to reconnect — emitting signals that could help search teams locate it. Even if the device uses MAC address randomization — a privacy feature designed to mask its hardware identity — Kennedy says the sniffer can “unmask” it using identity-resolving keys.
Still, success will require precision and some luck. “You have to be over the spot while transmitting to identify it,” Kennedy noted. Investigators would then need to triangulate the signal’s origin. If the pacemaker has been damaged or disabled, the technology would be ineffective.
Beyond aerial scanning, Kennedy has also developed companion iPhone and Android apps that could crowdsource the search. If authorities obtain the pacemaker’s specific hardware address, the app would allow citizens to scan for the signal and automatically relay potential matches to law enforcement.
“You could literally turn the entire community into scanning devices,” Kennedy said. “Hit ‘Find Nancy,’ and if there’s a signal, it tells authorities where to look.”
Nancy Guthrie was reported missing on February 1, and authorities have received between 40,000 and 50,000 tips. As the mystery deepens, investigators are blending traditional search efforts with cutting-edge cyber tools — hoping that somewhere in the digital noise, a faint signal may point the way home.
