Thread by @WIRED

On September 8, 2018, Karen Navarra’s heart rate apparently spiked and then plummeted. By 3:28 pm, she wasn’t registering a heartbeat. Navarra had been brutally murdered, and for five days nobody knew.

But there was a witness: Her Fitbit 1/
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Navarra’s Fitbit data wasn’t the only clue to her murder. Footage from a neighbor’s Ring camera showed a gray compact car in her driveway before and after 3:28 pm. It was the same size and color of a car driven by 90-yr-old Tony Aiello—her stepfather 2/
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Tony was 4’11” with hearing aids, a pacemaker with a defibrillator, and arthritis in his fingers. He told police he went over to Navarra’s to bring her biscotti and pizza. “She was alive when I left,” he said.

Adele, Karen’s mom, believes him 3/ wired.trib.al/OBJoIHj

Aiello’s lawyers say the Fitbit data is corrupt/unreliable. They pointed to one study which suggests that Fitbit's step-counting is only accurate about half the time. 4/ wired.trib.al/OBJoIHj

But tests of blood found on one of Tony’s jackets proved to be Karen’s. The chief trial deputy for Santa Clara County says that this, combined with the Fitbit data and Ring video, was “very strong evidence” against Aiello 5/ wired.trib.al/OBJoIHj

The Fitbit, Ring video, and blood point to Tony Aiello as the murderer. But his age and affable demeanor do not. Is a 90-year-old who “wouldn’t hurt a flea” capable of murder?

Is a Fitbit a reliable witness?

Our new cover story: wired.trib.al/OBJoIHj 6/