Lindsay Lohan and her handlers had hoped to keep her sobriety going with a special ankle bracelet that monitored her alcohol intake through her perspiration.

AP

Acress Michelle Rodriguez shows off her bracelet, on which she wrote "1984" and "Orwell" in protest.

Instead, the technology – ordered by Los Angeles County authorities and used by other celebrities trying to go straight – just helped chronicle her fall off the wagon.

The 21-year-old actress was arrested Tuesday after the mother of one of Ms. Lohan's assistants dialed 911 to report that she was chased by Ms. Lohan in her SUV. The assistant had quit her job just hours before, police said.

Police said the actress failed an alcohol breath test when they stopped her at 1:35 a.m. Her arrest came only two weeks after she left a rehabilitation facility in Malibu, Calif., following a DUI-related crash in Beverly Hills.

Since then, she had been seen around town and in paparazzi photos wearing the ankle bracelet, a high-tech device known as a Secure Continuous Remote Alcohol Monitor. It measures alcohol content emitted through perspiration in the skin and relays the information to authorities or, in this case, her attorney, Blair Berk.

Ms. Berk, one of Hollywood's top criminal attorneys, said she monitored Ms. Lohan's ankle bracelet's alcohol level regularly.

"Unfortunately, late yesterday I was informed that Lindsay had relapsed," Ms. Berk said Tuesday. "Addiction is a terrible and vicious disease."

Other stars have worn the devices under court orders. But Ms. Lohan voluntarily wore hers.

Since being launched in 2003, the ankle bracelets have helped keep 40,000 drinkers on the wagon, frequently as a condition of parole or probation for alcohol offenders, according to the Colorado-based manufacturer, Alcohol Monitoring Systems.

"We can't comment on or confirm any particular client. But if you have confirmation that someone is on an alcohol-monitoring bracelet, it would be ours," spokeswoman Kathleen Brown said a week before Ms. Lohan's latest arrest.

Most of the 43 states that have SCRAM programs require the offender to pay a $50 to $100 installation fee and a $10 to $12 daily monitoring fee.

Former state District Judge Vickers Cunningham asked Dallas-based Recovery Healthcare to start providing and monitoring the devices in 2003. The device is often too expensive for tight probation office budgets, so he had his defendants pay Recovery Healthcare themselves.

"I've been on the bench 11 years, and this is the best criminal justice tool I've ever had," Judge Cunningham said in 2005, shortly before he resigned to run for Dallas County district attorney, a race he lost.

But there is some debate about whether the bracelets really are effective, especially for those who have relapsed again and again. Critics say the bracelets won't prevent another offense; they just create a historic record of events.

"They don't prevent a person drinking and driving and endangering others," said Rebecca Lonergan, a University of Southern California law professor and former prosecutor.

Lindsay Lohan isn't the only celebrity to sport a SCRAM bracelet in public.

Tracy Morgan of 30 Rock wore one in early June while hosting the Guy's Choice Awards for Spike TV. He pleaded guilty to drunken driving in New York in February, a year after pleading no contest to the same charge in Los Angeles.

Michelle Rodriguez wore one during New York's Fashion Week in February. The former Lost star, who was charged with drunken driving in Los Angeles and Hawaii, derided it on her Web site as "a VCR Dog Tag."

Eve was ordered to wear one for 45 days after pleading no contest June 28 to driving with a blood-alcohol level above the legal limit. The rapper-actress was arrested in April in Los Angeles.