Thousands of ankle monitors that track the movements of sex offenders and other criminals were ordered removed and replaced by California officials because they were flawed and unreliable.
The Los Angeles Times says corrections officials began field testing GPS devices in late 2011. In April 2012, they ordered parole agents to remove every ankle monitor in use from north of Los Angeles to the Oregon border.
The Times says officials found problems ranging from inaccurate location reporting to failed tampering alerts that placed the public in imminent danger. It says in some cases, parolees might have been able to literally foil the devices by covering them with foil.
The devices were replaced by others from another manufacturer and state officials say the problems have largely been resolved.