SACRAMENTO — Electronic monitoring was supposed to help Los Angeles County deal with the influx of thousands of felons moved out of California's prison system to ease overcrowding.
The nation's largest probation department strapped GPS ankle monitors on the highest-risk of those convicts, expecting the satellite receivers to keep tabs on where they spent their days and nights, and therefore keep the public safe.
Instead, agents are drowning in a flood of meaningless data, masking alarms that could signal real danger.
County probation officers are inundated with alerts, and at times received as many as 1,000 a day. Most of the warnings mean little: a blocked signal or low battery.
The messages are routinely ignored and at times have been deleted because there were so many, officers say.
Auditors making a spot check last fall found more than a dozen cases in which officers failed to notice that the devices were dead and probationers roamed unmonitored, some for weeks.
"If we keep getting false positives, we're not going to know the real one that means danger," said John Tuchek, a vice president for the Assn. of Probation Supervisors.
California's statewide system for monitoring sex offenders sends out as many as 40,000 alerts each month to state parole agents.
The consequences of ignoring such warnings can be disastrous.
In upstate New York, federal probation officers deluged with false alarms opted to disregard tampering alerts that cleared themselves within five minutes.
Because of that, no one noticed last year when a man facing child pornography charges broke the strap of his monitor and slapped it back together with duct tape. The man left the still-operational device at home, then traveled across town and raped a 10-year-old girl and stabbed her mother to death.
A U.S. District Court judge in New York released a report in April noting that probation officers in 12 of the nation's 94 federal court districts routinely ignored short-term alerts. Federal court officials ordered the practice stopped.
In Colorado last year, officers dismissed days of tampering and dead battery alerts from a parolee's GPS monitor. The man had slipped out of the device strapped to his ankle and killed a pizza delivery man and the state's corrections chief, authorities said. The fugitive was shot and killed days later while attempting to flee police in Texas.
Proponents of GPS technology say improving the system is a matter of better training, smaller caseloads and more effective technology to filter the flood of data.
Steve Logan, chief executive of Satellite Tracking of People, which monitors California sex offenders, said officials and the public should not see GPS tracking as a panacea.
Electronic monitoring is "a tool … not a silver bullet, but a really, really good tool," Logan said.
But some national GPS experts and parole officers say there are so many technological problems with GPS monitoring that it will never be as secure as officials promise.
"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 Assn. and coauthor of the Justice Department's guide on electronic monitoring.
"In some ways, GPS vendors are selling law enforcement agencies, politicians, the public a false bag of goods," he said.
The data overload disclosure comes as nearly every county in California is preparing for a massive expansion of the "virtual jail" — the use of GPS devices to track criminals on the street rather than incarcerate them.
The growth is being driven by a federal court order requiring the state to reduce prison crowding. In two years, California shifted more than 100,000 state inmates and parolees to local control.
The influx has required the release of lower-level criminals to make room, meaning county probation departments must monitor an increasingly dangerous population.
Last year, then-L.A. County Sheriff Lee Baca solicited bids from GPS tracking companies to monitor as many as 3,000 offenders released from jail, while the county Probation Department is using GPS to track hundreds of felons released from prison. Riverside County has approved $1 million to monitor up to 600 criminals.
California began using GPS tracking in 2008, when voters passed Jessica's Law, which required round-the-clock monitoring of serious sex offenders. More than 8,000 state parolees continue to be tracked under that law.
The basic systems involve a device strapped to a person's ankle. The monitor picks up satellite signals and transmits location information over cellular networks to a central computer.
The system is designed so that an alert is sent out if an offender tries to remove the device or enter a forbidden area, such as a school or park. But notifications go out for a variety of routine reasons, as well: GPS signals are blocked by buildings, batteries run down, cases crack and straps come loose.
There is no easy way to distinguish the cause of a notification. A prolonged lost signal might mean an escape or merely a signal blockage inside a mall.
Field tests by California corrections officials in 2011 showed the devices used to track nearly half of the sex offenders in the state reported no signals 55% of the time — blind spots the manufacturer attributed to buildings, cars and trees.
In most cases, each anomalous event prompts an alert to the supervising officer.
The number of emails is compounded by another stream of data: The county Probation Department sets its system to trigger an alert whenever a device passes a school or park.
More than 4,800 prohibited areas are designated in L.A. County, about one every square mile. That makes it difficult for an offender to go anywhere without causing a string of alerts — a total of 7,500 messages generated by about 300 probationers each month.
"Just riding the Red Line would set off 10 alerts, passing schools on the way," said Tuchek, the union official who also works as a county probation supervisor.
One recent log showed that 65 offenders racked up 135 alerts in a single overnight shift. None resulted in an officer's response, and the probation office wrote off one felon's string of seven tamper alerts as a possible equipment malfunction.
The email overload was made even worse because of a policy that until recently required all alerts to be sent to every probation officer supervising someone via GPS.
The combined effect, department administrators said, was that deputies on some days were greeted by more than 1,000 new alerts in their email in-boxes.
"If the probation officer receives thousands of emails for every probationer in the county, he will delete them all without reading any," said one deputy who did not want to be identified because he was not authorized to speak on the issue.
A department audit in September documented numerous cases in which alerts went unheeded. Officers, according to the audit, were unaware their charges were not being tracked for days at a time. One offender went untracked for 45 days.
Reaver Bingham, deputy chief of the county Probation Department, said most officers try to discern the most serious messages in the flood and concentrate on those.
In November, the county stopped blasting out group alert messages to reduce the email overload. Still, the system generates more than 20,000 messages a month.
Sentinel Offender Services, the Irvine-based company that provides L.A. County's GPS monitoring system, refused to comment on the program. However, in a 28-page corrective action plan sent to the county in November, Sentinel's chief business development officer, Mark Contestabile, discussed "the onslaught" of alerts.
The frequency of the alerts is "overwhelming to the officer," Contestabile wrote. "This is an area of the program that must be addressed as we move forward in program development."
Dwight Thompson, a field representative for the union representing county probation officers, said reducing the number of alerts won't solve all the system's problems.
Officers, he said, rarely have the time to check out even a lower number of alerts. "How do you drop everything else to find out why" an alarm has gone off, Thompson said.
And he said probationers are well aware there is seldom a response when a device does go off: The department lost 80 offenders in 2013 who cut off their GPS monitors and disappeared.
"If a person's not being properly monitored or supervised, then what's going to stop them from taking it off and leaving?" Thompson asked. "If they take it off, what was the point of putting it on?"