Dennis Gilbertson chuckles when he recalls the first time Hennepin County corrections officials got solid proof that their new alcohol detector worked as promised.

Only hours after an offender was outfitted with the new home monitor, alerts signaling an infraction popped up on the county workhouse monitor in Plymouth. The man was called in for a Breathalyzer test, found to have a blood-alcohol content of 0.14 percent and sent back to the workhouse.

It's called a transdermal alcohol detector, a big name for a little device that's transforming how corrections officials keep tabs on community-based offenders who shouldn't be drinking.

It was launched last fall by BI Inc. of Boulder, Colo., and has just arrived in Minnesota, with the promise of saving time and money for county officials used to less-efficient means of monitoring offenders.

Two months after the device was introduced in Hennepin County, nearly 200 adults on electronic home monitoring are wearing the detector. So far it has fingered 16 scofflaws. Gilbertson said there also have been a couple of false alarms owing to alcohol-based spray, such as deodorant or perfume, or misinterpretation of data.

The detector, which resembles a small black camera, also notes whether offenders are home when they're supposed to be. If not, or if they try to disable the device, the workhouse is alerted.

"It's an enhancement to community safety because it's been pretty reliable so far," said Gilbertson, workhouse superintendent. "This is the direction that folks are going, using technology to enhance our ability to supervise [offenders]."

Real-time information

With a battery-powered sensor strapped 24/7 to the ankle, the waterproof detector can sniff out alcohol either through sweat or vapors rising from the skin.

If even a trace is found, the news is flashed via radio frequency to staff members at the workhouse. They can then take steps to confirm the report and detain the offender if necessary.

"It gives us real-time information that someone's using alcohol," said John Ekholm, a manager with the county's community offender management program.

Gilbertson said the device offers advantages over previous means of monitoring, which consisted of voice recognition equipment and regular breath tests. The transdermal detector takes only 15 minutes to set up, about a third of the time of earlier methods.

It also helped ease the adjustment that the corrections department faced last January when the minimum-security work release building was shut down, in part because of budget cuts.

The county has budgeted about $500,000 to rent the monitoring equipment from BI Inc. Gilbertson said the county recoups "a significant portion" from offenders who have the means to pay the daily $8 rental fee.

The detectors are monitored around the clock by five to six staff members who have added that task to their other assignments, he said.

Another tool in the arsenal

BI Inc. calls the transdermal detector "a pioneering device" because it picks up "drinking events" from the skin sensor and reports them to a headquarters monitor, using equipment attached to a phone in the offender's home.

About 1 percent of alcohol leaves the body in the form of sweat or vapor, and it takes longer for alcohol to reach perspiration than it does the bloodstream.

For that reason, after an offender takes a drink there may be a delay of 30 minutes to two hours before it's reported by the transdermal device. Those results must be confirmed by a subsequent breath or urine test.

The company promises a 99 percent accuracy rate.

"We have other alcohol monitors, and because of the technology, this is a far superior product to what we've offered in the past," said Monica Hook, a BI spokeswoman. "This enables agencies to have one more tool in their arsenal."

After six months, county officials will analyze how well the detectors have worked, Gilbertson said. It's too soon to know whether Hennepin County will make a long-term commitment to the transdermal detectors, he said, but so far results are promising.

"I think everybody feels better in having something to help us determine whether [offenders] are following our rules or not," he said.

Kevin Duchschere • 612-673-4455