Once a convicted sex offender is released from prison in California, authorities attach a GPS monitoring device to the parolee’s ankle in order to monitor their movements. But the system, officials realized last year, was badly flawed, leaving the public “in imminent danger” from thousands of rapists and child molesters who had figured out how to compromise the devices.

The California Department of Corrections & Rehabilitation began testing the GPS devices in use last year, and found they couldn’t reliably track sex offenders residing anywhere north of Los Angeles.

The problems with the equipment were many. Batteries gave out sooner than expected, locations of parolees were off by miles, and many sex offenders figured out ways to tamper with or jam the GPS systems. At the urging of corrections attorneys, this information was sealed by a judge, reportedly to avoid “erod[ing] public trust” and to ensure that offenders continued to believe that they were constantly being tracked by a flawless system.

Officials took action and—leaving the tracking system down for several hours—replaced every ankle monitor used in Central and Northern California with new ones produced by a different company.

The state claims it has fixed the problem, but hasn’t released any data to back up this assertion.

In California, there are currently 7,900 high-risk parolees—most of whom are sex offenders or gang members—who are fitted with GPS trackers.

-Noel Brinkerhoff

To Learn More:

Tests Found Major Flaws in Parolee GPS Monitoring Devices (by Paige St. John, Los Angeles Times)

Alarming Ankle Monitor Findings (Los Angeles Times)

Parolees, Taking Advantage of Overcrowded Jails, Are Ditching GPS Tracking (by Ken Broder, AllGov California)