Skip navigation
× You have 2 more free articles available this month. Subscribe today.

GPS Monitoring System in Los Angeles Plagued by False Alerts, Ignored Alarms

Los Angeles County’s GPS monitoring system, designed to keep track of high-risk probationers, has overwhelmed probation officers with thousands of false alerts each day – so many that some officers simply ignore them. As a result, dozens of probationers have been able to roam unmonitored. In some cases, even when probationers removed their monitoring devices, the removal was not discovered for lengthy periods of time.

GPS monitors are used to track the highest-risk probationers and parolees, including sex offenders. A massive shift of prisoners from state prisons to county jails under California’s “realignment” legislation has led some counties to release hundreds of low-level offenders on electronic monitoring as a way to cut costs and reduce jail overcrowding.

The GPS system in Los Angeles County picks up satellite signals and transmits the data over cellular networks to a central computer. The system is designed to send an alert to a probation officer under a variety of circumstances; for example, if a probationer tries to remove the monitor or enter a designated prohibited area, or if the GPS batteries run down. The GPS devices send alerts for a number of routine reasons, too, such as when the signal is blocked by a building or if the monitor has a loose strap or damaged case.

According to probation officers, there is no easy way to distinguish the cause of the alert. Thus, a prolonged lost monitoring signal might mean the probationer has absconded or simply that the signal is being blocked due to a building’s structure.

County officials say they have been “overwhelmed” with thousands of alarms each day. Most are relatively meaningless, for low battery warnings or blocked signals, and are ignored or deleted by probation officers. Others are more serious; 80 probationers removed their GPS devices in 2013, and in one case an offender went unmonitored for 45 days.

“If a person’s not being properly monitored or supervised, then what’s going to stop them from taking it off and leaving?” asked Dwight Thompson, a representative for the union that represents Los Angeles County probation officers. “If they take it off, what was the point of putting it on?”

A field test in 2011 found that GPS devices used to monitor California sex offenders transmitted no signal 55 percent of the time, and PLN previously reported that thousands of sex offenders in the state had removed their GPS monitors or committed monitoring violations, as there were few repercussions for doing so. [See: PLN, April 2013, p.18].

A November 13, 2013 corrective action notice sent by the Los Angeles County Probation Department to Sentinel Offender Services, the company that provides the county’s GPS system, indicated that one in four GPS devices were faulty – they generated too many false alarms or had defective batteries. Sentinel blamed poorly-trained probation officers and probationers who didn’t follow instructions for properly charging their GPS monitors. [See: PLN, Jan. 2014, p.18]. The company has increased training and replaced the monitors with more recent models.

Private companies that provide GPS monitoring services may be more interested in generating profit than ensuring public safety – one of several concerns related to the increased use of electronic monitoring. [See: PLN, March 2012, p.20].

While faulty equipment doesn’t help matters, Los Angeles County also has the GPS system set up to send an email alert to a probation officer when a probationer passes through, or travels close to, a prohibited area – such as when sex offenders are near schools or parks. There are some 4,900 prohibited areas in the county, about one every square mile. This makes it almost impossible for a probationer to go anywhere without triggering alerts, and thousands of those alarms are generated each month.

“Just riding the Red Line [public transportation] would set off 10 alerts, passing schools on the way,” noted John Tuchek, a vice-president for the Association of Probation Supervisors who also works as a probation officer. “If we keep getting false positives, we’re not going to know the real ones that mean danger.”

“When these alerts are in the tens of thousands, it seems like an unwinnable situation,” said Matthew DeMichele, a former researcher for the American Probation and Parole Association, and coauthor of the Justice Department’s guide on electronic monitoring. GPS monitoring systems simply don’t provide the level of accountability and security that they claim, he added: “In some ways, GPS vendors are selling law enforcement agencies, politicians, the public a false bag of goods.”

Sources: Associated Press,,,

As a digital subscriber to Prison Legal News, you can access full text and downloads for this and other premium content.

Subscribe today

Already a subscriber? Login