Diane Rosenfeld believes many domestic violence homicides are preventable. “We know exactly who the victim is,” she says, as opposed to say, child molesters, who could prey on any number of children in any number of places. With domestic violence, the intended target is much clearer.

That’s why Rosenfeld, the director of the Gender Violence Program at Harvard Law School, has been working for almost a decade to more widely implement the use of GPS tracking on convicted domestic violence offenders. Think ankle bracelet, but more advanced.

“It’s an ankle bracelet with a phone in it so a probation officer or police department can speak to the offender,” she explains. Say “Mr. Jones,” a convicted domestic violence offender, traveled outside the boundaries he was allowed in. The device might say, “Mr. Jones, you’re out of your zone,” says Rosenfeld. “He could say he was lost, but the GPS shows he’s going toward his ex-wife’s house. We would be able to alert the survivor immediately and tell her not to open the door and, simultaneously, send police.”

Rosenfeld says this GPS technology is currently being used in 23 states, with 11 more states pending legislation to put it in place. On the forefront of that movement is Connecticut, one of the first states to use GPS tracking on high-risk domestic violence cases since 2004. Rosenfeld, working with the Greater Newburyport High Risk Case Management Team, implemented GPS tracking as part of an overall containment model. And, it worked. “They have had no domestic violence-related homicides in the areas they’ve served in 11 years. It can really save lives.”

Similar GPS tracking has been proven effective in preventing repeat criminal offenses from high-risk sex offenders. Research found that of 516 offenders released on parole in California between 2006 and 2009, those under parole supervision but who were not fitted with a GPS-enabled ankle bracelet were 38 percent more likely to return to custody than those on the tracking system.

The downfall is cost. The National Institute of Justice found that monitoring sex offenders with GPS costs approximately $36 a day per person, while traditional “supervision” is only $27 per day. However, the payoff is fewer arrests and higher parole compliance. For Rosenfeld, the benefits clearly outweigh any price tag. “It catches violations of orders of protection which previously had been impossible to catch. Maybe [a survivor] sees her batterer drive by but wasn’t sure, so she doesn’t call police. He’s trying to see how much he can get away with. [With GPS tracking], now it’s not just her word against his.”