Ankle Monitors On High-Risk Offenders Malfunctioned For Years, Officials Found

California has discovered GPS devices strapped to ankles of recently released sex offenders and gang members malfunctioned for years — meaning the criminals' parole officers had no idea where they were, the L.A. Times reported.

When officials began testing the anklets used to track 4,000 offenders in late 2011, they found a variety of problems: cracked cases, batteries that died early, and locations that were off by as much as three miles, according to the Times.

The Times uncovered the results of that testing through interviews and documents from a recent lawsuit over the state's GPS contracting.

3M and another company, STOP (Satellite Tracking of People), manufactured the anklets used to track high-risk parolees and sex offenders across the state.

Corrections officials said the anklets made by 3M were so unreliable that the public was in "imminent danger," according to the Times.

In late 2011, parole agents began testing the devices by submerging them in water, dropping them onto concrete, and moving them out of reach of cell phone and satellite signals, the Times reported.

California voters approved the statewide monitoring program in 2006 that required all sex offenders to wear anklets for the rest of their lives.

The revelations of allegedly faulty anklets come after the LA Times found in its own investigation that thousands of paroled child molesters, rapists, and other high-risk criminals were disabling their GPS anklets.

3M did not immediately respond to two requests from Business Insider for comment on its anklets.