Ankle bracelets are often used for monitoring the location of a criminal defendant who has either been released on bail or, after being convicted, is on probation. Many of these bracelets are also equipped with technologies that allow them to monitor the alcohol consumption of the wearer. (Also, read about drug-test patches.) This article will give a brief summary of how these secure continuous remote alcohol monitoring (SCRAM) bracelets work, the science behind them, and when they might be required.
When alcohol monitoring is ordered by a court it is generally as a condition of bail (sometimes called "bond") or probation. Courts typically order SCRAM bracelets only in DUI/DWI cases and other cases where the offense involved drugs or alcohol. However, there might also be situations where a court would order SCRAM when, although the current offense didn't involve drugs or alcohol, the offender has a history of substance abuse.
Whether ordered as a condition of bail or probation, the purpose of a SCRAM bracelet is the same: to ensure the defendant does not consume any alcohol. In many cases, the judge orders a SCRAM bracelet in lieu of jail time. With the SCRAM bracelet, the judge can ensure the defendant isn't drinking alcohol, and if the defendant does drink, the device will report a violation. A violation could result in revocation of probation or release on bail.
When a SCRAM is required, the defendant is usually responsible for picking up the cost. Installation might run anywhere from $50 to $100, and monthly monitoring fees can be up to $300 or more.
Any time alcohol is consumed, it ends up going somewhere: Most is metabolized, some is processed and expelled by the kidneys and a small amount (about 1%) is actually secreted from skin pores. The alcohol secreted from the skin pores can be monitored via transdermal (through the skin) testing. Once the alcohol evaporates through the skin, a fuel cell within the SCRAM device measures the amount of ethanol gas within the insensible perspiration (vapor).
Using transdermal testing, the bracelet obtains a sample of evaporated sweat every 30 minutes or so and sends a report to the monitoring agency. If alcohol is present, the agency will notify the appropriate court, police, or agency responsible for supervision. The bracelet does not record an exact blood alcohol concentration (BAC) level, but instead provides a report of drinking "incidents" and the peak concentration therein. And before attempting to tamper or remove the device, take note that the SCRAM bracelets have several anti-tampering design features that can detect if the device has been modified or tampered with.
While the data that comes from SCRAM bracelets is generally accepted as accurate and admissible in courts, errors are possible. Using certain products, such as rubbing alcohol, might lead to a false positive. Also, some doctors have expressed concern about the use of SCRAM bracelets by those with certain medical conditions such as a history of stroke or heart defects.