In orbit 13,000 miles above earth, 24 US military satellites with atomic-clock hearts cycle the earth twice a day. They’re monitored and adjusted from ground stations across the planet. These two components, along with the commercial devices available in any tech store, make up the Global Positioning System—a public utility owned by the US government.
A GPS device finds its position in space—latitude, longitude, altitude—by locating four satellites in orbit. It calculates the distance between the quartet to triangulate a point.
GPS was used exclusively by the US military until 1983. That fall, Korean Air Lines Flight 007—New York to Seoul, via Anchorage—drifted into Soviet airspace. It was shot down, killing 269 passengers and the flight crew. In response, President Ronald Reagan ordered the GPS open to civilian use, with the hopes that the technology could prevent future catastrophes.
Twenty-four years later, the planet’s dependence on the system means that GPS failure would be a global security emergency, not only for air traffic, but for tracking and targeting missiles and monitoring conflict zones.
In New Mexico, it would mean 80 sex offenders under state supervision would be freed from their electronic balls and chains.
Most of the GPS units placed on sex offenders come in two parts: a light-weight ankle bracelet and a five-pound box that can be worn around the waist or over the shoulder with a strap. An offender must have both devices with him at all times.
The ankle bracelet serves only as an electronic tether to ensure the inmate is always within a few feet of the primary GPS unit. That box triangulates its position and then sends that information through regular cellular signals to the monitoring station. This transmission is where many of the glitches originate.
The devices can transmit an infraction message within 15 seconds. Common violations include “Bracelet Gone” and “Strap Tamper,” but the device also alerts law enforcement if there’s a curfew violation, if the offender has strayed outside his imposed “inclusion zone” or wandered into the “exclusion zone,” which could be a school, a park or a victim’s neighborhood.
While these violations often prove real, they are also frequently false. Santistevan says he’s watched the device register a “device gone” alert while an offender sat across from him in his office. Snowstorms also interfere with the signal and Santistevan has had to continue
the session in the parking lot while his client tries to reestablish connection.
“Usually, [the alert] will clear, but we’re still standing out there in the snow for 30 minutes,” Santistevan says.
According to Terry Baker, the parole and probation officer who exclusively handles sex offenders in Santa Fe, cloud cover can interrupt the signals and there are several dead zones in Lamy. Sometimes the satellites themselves are glitchy.
“If a guy is at work at a warehouse, sometimes the GPS will show him 1,000 yards away one minute, and the next minute he’ll be back at work,” Baker says. “You know he can’t cover 1,000 yards in a minute.”
This, he says, makes filtering the true violations from the false ones difficult. But that’s to be expected with a first-generation device.
“We’ve got newer models coming down the pipe that I hope will iron out some of these false positives,” Baker says. The new devices are one-piece GPS ankle bracelets, and he is already testing one with a parolee.
Right now the state holds an $87,000 contract with Florida-based Pro Tech Monitoring, which provides the devices and software, and maintains an archive of all offender data. The state rents the individual units at a rate of $8.45 per offender per day, the equivalent of more than $3,000 per offender per year.
The offender pays only a fraction of that: $50 per month, but if the device is damaged, lost or thrown away, he is liable for the full cost: $1,500.
That’s too much for most offenders, Tennant says.
“If they’re going to run, they’ll often drop the GPS off [at night],” he says. “We’re not open then, but they just drop it outside the front door.”