NOT every criminal offender talks about wearing an electronic monitoring device quite the way 16-year-old Ronnie does. "It started out as an uninvited guest at the dinner table but turned into a guardian angel," says the youth from Winston-Salem, N.C.When he and his mother first left the courtroom and he saw the ankle bracelet "my whole leg was shaking," he says. "After two or three days I forgot about it. But I never forgot what I had to do to get it off." Ronnie (not his real name) had to wear an electronic home-arrest bracelet for four weeks. When it came off, he had proved his desire to change his ways. If it was time for him to go home early he would tell his friends (without losing face) by just pointing to his ankle. He could also tell them that vandalizing cars and breaking into houses wasn't smart. The juvenile court still keeps tab on him and will do so for a probation period. His story is not unique. Preliminary reports from the first wave of national studies done since state and county corrections departments introduced the home-arrest devices some six years ago give rise to modest optimism, say corrections officials. Plagued by prison overcrowding, budget cuts, and high recidivism, "It is a very good tool in the correction's box," says Joseph Vaughn, associate professor of criminal justice at Central Missouri State University in Warrensburg, Mo., and editor of the journal Electronic Monitoring. "One of the things that really struck us" after looking at the data on electronic detention programs, says Terry Baumer, associate professor of public affairs at Indiana University, Indianapolis, "was the high number of positive comments we got from offenders after they finished the program." Individuals who had lifestyle problems - from alcohol and drug abuse to carousing too much - made comments like, "I stopped drinking.... My wife thinks its great.... Haven't missed a day of work in six months." Electronic monitoring is an intermediate sanction between parole and prison. Most home-incarceration programs started out by emphasizing surveillance and security but neglected rehabilitation, Professor Baumer says. "This aspect must be looked at more closely" now, he says. The concept of electronic monitoring appeals to both liberals and conservatives, says Tim App, director of community corrections in Massachusetts. For those who want to get tough on crime it allows offenders to be restrained who might otherwise walk free because of overcrowded prisons and the fact that their crime isn't as serious as others who tie up scarce cell space. For those who think the United States has already gone too far with its incarceration rate, electronic monitoring can be used for offenders who might otherwise be kept in jail or prison without needing so severe a sanction. The first thing to note about electronically monitored home detention is the distinction between the sanction (home detention) and the method (electronic monitoring). Keeping the two aspects separate, says Professor Baumer, assists in a realistic appraisal of the appropriate use of home incarceration. Electronic monitoring programs rely on the threat of immediate detection and subsequent sanctions for unauthorized absences. Given that there are no physical restraints when an individual is sentenced to his or her home, the burden of responsibility falls heavily on the corrections agency to target individuals who are unlikely to pose a serious threat to others, Mr. App says. Only inmates with three or fewer months of time remaining on their sentence can be in the Massachusetts program. Of the first 100 individuals in the program, five were returned to prison to complete their sentence, he says.According to the National Instit ute of Justice, it costs anywhere from $60,000 to $75,000 per bed to build a prison and $60 per day per inmate to operate it. Home-arrest equipment costs between $4,500 and $5,000 per inmate and anywhere from $8 to $18 per inmate per day to provide the monitoring, depending on the level of oversight a jurisdiction wants to provide. The savings are even greater, App says. Since the inmate is out in the community and working, he or she is required to pay for rental and use of the monitoring equipment. And this is in addition to whatever taxes the offender is paying, he says. All 50 states employ some version of electronic monitoring. There are 435 adult programs in the US, with the greatest number in Florida and Michigan. Texas and California are coming up the fastest. Juvenile programs are much smaller and this is typical (since juvenile programs traditionally follow adult programs), says Professor Vaughn. No one knows what the high end for use of electronic monitoring will be. "We're still at its infancy," he says. "Electronic monitoring is a tool. It is not a program in and of itself. It cannot be a substitute for sound correctional policy making," App says.