As Tony Aiello entered his nineties, he had false teeth, an artificial hip, and an artificial knee. He gripped a walker to hoist himself out of bed. Stiff in the back, he had contraptions to help him pull on his pants and socks, along with a shoehorn to slide his feet into velcro-strapped shoes. He had hearing aids and a pacemaker with a defibrillator for his triple-bypassed heart. He would read recipes in the living room and forget the ingredients by the time he reached the kitchen. Arthritis stiffened the fingers that had served him for decades as a deli butcher, so he cut food with scissors. He took blood thinners for his congestive heart failure. The slightest nick while pruning trees in the yard would make him bleed until his wife, Adele, would, as he put it, “patch me up.” After losing an inch or so to age, Tony stood 4'11".

Still, Tony would brag, “Nobody believes that I'm 90.” He could do anything—“a little slower.” Perhaps that was just Tony being Tony. People who'd known him for decades said he'd always had “little man syndrome.” But maybe there was something to the bravado. Neighbors said that not so long ago, Tony seemed hale—a stocky figure walking down the sidewalk in a tank top, like a pint-size, sure-stepping Marlon Brando. He was gutsy too: When he was about 80, he met Adele Navarra while they were in line at the Save Mart meat counter and asked her to coffee the same night. He bought two dozen roses for the occasion.

Both Tony and Adele were widowed, and before long they married. Adele was two years Tony's senior, but people marveled at how sharp she was. She moved into Tony's house in the Berryessa neighborhood of eastern San Jose, California. By chance, her daughter, Karen, lived just two blocks down the street. Once, when Adele fell in the yard, a neighbor who came to her aid noticed that Tony seemed just as doting as could be as he helped her back into the typical ranch home on a typical San Jose block where, by all appearances, he'd lived a rather typical life for the past 50-plus years.

Then, on September 14, 2018, a coroner's investigator came to the house and broke anguishing news: Adele's daughter, Karen, had been found dead.

October 2019. Subscribe to WIRED. Photograph: Dan Winters; Typography: Claudia de Almeida

Karen was 67 and lived alone with her two cats in a house on Terra Noble Way. She worked as a pharmacy tech at a San Jose hospital, and when she didn't show up for work, a coworker stopped by to check on her. The front door was unlocked, and, once inside, the coworker found Karen's corpse in a chair at the dining room table, her legs stretched out, her head slumped over the chair's back, bloody from bash wounds that an attorney would later say “destroyed her identity.” Her right hand clutched a Flint kitchen knife with an 8-inch blade. Her throat was slit, twice.

The investigators who arrived saw no telltale spatter of a throat-slashing; the slice had happened after she was already dead. In fact, it looked not only as if the scene had been staged but ham-handedly so, without a clear idea of the faux plot. The knife in Karen's hand seemed to suggest suicide, yet the knocked-over chairs indicated a struggle. Her bedroom and kitchen drawers were open or on the floor as if ransacked, but the drawers were neat, their contents intact, with cash, jewelry, and electronics still in the house, financial documents on the kitchen table.

The criminal oversights didn't end there. As Karen's body was unzipped from the body bag and laid out at the morgue, the coroner took note of a black band still encircling her left wrist: a Fitbit Alta HR—a smartwatch that tracks heartbeat and movement. A judge signed a warrant to extract its data, which seemed to tell the story Karen couldn't: On Saturday, September 8, five days before she was found, Karen's heart rate had spiked and then plummeted. By 3:28 in the afternoon, the Fitbit wasn't registering a heartbeat.