They monitor heart rate and the number of steps taken, but who would have thought fitness trackers could also reveal pertinent facts in a criminal case?

24-HOUR MONITORING

What many people don’t know: Fitness trackers are always recording and never forget. If your heart rate climbs because you’re involved in an argument, that gets recorded too. The data only indicate that your heart was beating faster, of course, and not the reason why.

WHAT FITNESS TRACKERS ARE TRACKING

Steps taken, heart rate, blood pressure, calorie consumption, sleep stages: Fitness trackers record data about the wearer’s body and activities as well as locations. That makes it possible for you to know how far you’ve walked or jogged, how your heart rate was affected, and how well you slept last night.

FLAWED DATA PROTECTION

Although the fitness tracker market is booming, the devices do have some shortcomings. In addition to the problem of inaccuracy, data protection is also a serious deficiency. How is a user to know who has access to the recorded data? Fitbit, for example, says it does disclose data to comply with applicable laws and governmental demands, which vary from country to country.

Fitness trackers are small and inconspicuous, but the data they collect reveal a lot about those who wear them: the state of their health, where they were and when—even the moment of their death. So in a murder case, the device can become an important witness…

Everybody who knew Anthony Aiello described him as a kind and amiable person. The only thing his neighbors could criticize about him was that his life seemed rather boring. Anthony “Tony” Aiello had lived for 50 years in the same house in the city of San Jose, California, and in retirement he seemed perfectly content to enjoy life with his second wife, Adele. His “boring” existence may have been influenced by the growing number of medical conditions with which he had to contend: congestive heart failure, arthritis, and an artificial hip. But Tony seemed to take everything in stride: “No one can believe that I’m 90,” he used to say. He had met his second wife a few years earlier at the meat counter of the local supermarket. Adele was two years older than Tony and, like him, she was widowed. For her it was love at first sight, and soon she’d moved in with him. The move proved practical because Adele’s daughter, Karen Navarra, lived only two blocks away. For 10 years the Aiellos enjoyed a good life together, but everything changed suddenly on September 14, 2018. That’s when the police came to tell Adele that Karen’s body had been found at her house. She’d been murdered.

THE LAST VISITOR

Karen Navarra hadn’t come to work at the pharmacy for several days, and her co-worker was starting to worry. It simply wasn’t like the 67-year-old pharmacy technician to miss work without saying anything, so her friend decided to check on her. When she arrived at Karen’s house, she found the door was unlocked, and that only added to her uneasiness. The scene she discovered inside was appalling: Karen was slumped over in a chair, holding a big kitchen knife in her right hand, and she had serious wounds across her head and neck. There was pizza on the kitchen counter and on the floor. Her friend called the police, who were initially confused by what they were seeing. The knife in Karen’s hand suggested suicide, but there were other signs that there had been a struggle. When the coroner ruled the cause of death to be homicide, police investigators concluded that somebody was trying to cover up a crime. They first sought out Tony and Adele, since they were Karen’s only known relatives. After waiting for the initial shock to settle, they began their interrogation. It soon became clear Tony was probably the last person to see Karen alive. He admitted visiting her on the afternoon of September 8 to bring her pizza and biscotti. When he was asked if he could remember any other details, Tony said that Karen had mentioned going out with friends that evening. “Did you say friends or a friend?” asked an investigator. Tony said he couldn’t remember for sure, but he did recall that Karen had driven past his house later that day and a man he didn’t know was sitting beside her in the car. As Tony was providing his statement, Adele recalled Karen recently telling her that she had seen a man several times who seemed to be watching her from the other side of the street. Karen had said that this frightened her.

The case was becoming clearer: The police now suspected Anthony Aiello was possibly not just the last person to see Karen alive but also their most important witness. He had probably seen the killer. Given Tony’s testimony, the investigators started looking for surveillance cameras in the neighborhood that might have recorded something revealing. And they were in luck: There was, in fact, a surveillance camera with a view of the victim’s driveway. The problem: The videos didn’t show an unknown man, nor did they show that Karen had left her house that afternoon. They showed a Toyota parked in the

“THAT NICE OLD MAN WOULDN’T HURT A FLY.”

driveway of the house from 3:12 to 3:33 on the afternoon of the murder— Tony’s car. The situation seemed as confusing as ever. But then the police received information that opened up a new line of investigation and yielded an entirely new suspect…

VITAL WITNESS

Up until this point, the police hadn’t told Tony and his wife a crucial detail: Karen had been wearing a Fitbit at the time of her death. Because fitness trackers are constantly recording the wearer’s heart rate and transmitting their data to the company’s servers, the investigators asked Fitbit to send them Karen’s data. They were hoping that some aspect of the information would be the key to solving the case. And indeed: The data showed Karen’s heart rate had accelerated swiftly at 3:20 P.M. before decreasing sharply. At 3:28 it had abruptly stopped. This was within the time frame that Tony’s car was parked in front of the house. That changed everything: Suddenly Karen’s stepfather was not merely a witness; he was the prime suspect.

Not long after, Tony found himself sitting in a police interrogation room. “What the hell am I doing here?” he’d asked the detective, who replied to his question with a question of his own: “Do you know what a Fitbit is, Tony?” Aiello shook his head. “It’s a watch with a heart rate monitor built into it.” Aiello didn’t understand. “According to Karen’s Fitbit, her heart stopped beating at 3:28 P.M.,” the detective explained. “And we know that you were still in her house at that time.” The nonagenarian stiffened. “That’s impossible,” he stammered. “Karen was still alive when I left. Someone else must have been in the house… or the thing wasn’t working right.”

THE BODY’S BLACK BOX

Is that possible? Could the Fitbit have been wrong? The fact is: Since Fitbit was founded in 2007, the market for health apps and the equipment that goes with them has been growing by leaps and bounds. From 2010 to 2019 Fitbit’s sales rose from 60,000 units to 16 million. Given this widespread use, it was inevitable that sooner or later a crime victim or suspect would be wearing one when the crime was committed, thus potentially providing investigators with important data. In 2015, a woman had alleged that an intruder in the home where she was staying raped her. There was a Fitbit on the floor at the scene, and it helped investigators determine what really happened. They discovered that the woman’s statements did not line up with the Fitbit’s data and that she had to be lying about the incident. In 2017 a Fitbit helped police solve a murder case: When a woman was killed at home, her husband told the police that an intruder had broken into their house and shot his wife. Her Fitbit, however, showed that she had been at the gym at the time her husband

SUDDENLY KAREN’S STEPFATHER WAS NOT MERELY A WITNESS; HE WAS THE PRIME SUSPECT.