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SCRAM—Alcohol Monitoring Ankle Bracelets

By Grizopoulos & Portz, P.C. with the approval and consent of Patrick Barone

The SCRAM (Secure Continuous Remote Alcohol Monitor) ankle bracelet measures the amount of alcohol in a person’s body “transdermally,” meaning that it tests the amount of alcohol in the perspiration after it passes unmetabolized through the skin. The idea of using perspiration for measuring bodily alcohol content goes back to the 1930s, and several studies during the last three decades have shown that there is a fairly good correlation between perspiration alcohol and blood alcohol. See Davidson, et al., “Behavior Effects and Pharmacokinetics of Low-Dose Intravenous Alcohol in Humans,” 21 Alcoholism: Clinical and Experimental Research 7, at 1294 (Oct. 1997).

The SCRAM device is manufactured by Alcohol Monitoring Systems (AMS) based in Highlands Ranch, Colorado, and is currently used in 49 states. It is small enough to be worn continuously underneath clothing, and this smaller format allows the perspired alcohol to be discretely measured. The device produces qualitative measurements and can remain in use for large periods of time.

The SCRAM bracelet is most often used by courts to monitor an offender’s use of alcohol when such use is prohibited as a bond condition or a condition of probation. In many instances a confirmation of a drinking episode via the SCRAM bracelet will form the sole basis for a court’s determination that the offender has in fact consumed alcohol.


Due to ethanol’s affinity for water, it is rapidly distributed throughout the body by process of diffusion. Equilibrium occurs when all the fluids of the body will contain ethanol in close proportion to their water content. It can be assumed that there will be a relatively constant ratio between blood alcohol and perspiration alcohol so that despite relatively large concentration differences, the amount of alcohol excreted in the perspiration will parallel that in the blood over the entire excretion phase (rising and falling). This assumption underlies the use of perspiration to predict blood alcohol content. See Brown, “The Pharmacokinetics of Alcohol Excretion in Human Perspiration,” 7 Methods and Findings Experimental Clinical Pharmacology 10, at 539 (Oct. 1985).

However, transdermal monitoring for alcohol presents a variety of challenges, particularly as it pertains to obtaining reliable quantitative measurements. For example, unlike breath, blood and urine, the manner in which alcohol passes through the skin (pharmacokinetics) is not well understood. This lack of understanding is partly caused by the comparatively larger number of variables that are involved in this passage. These variables include the subject’s blood alcohol level and body temperature, the rate of diffusion through the skin, the skin type and location, the thickness of the stratum corneum (the major barrier to water), the amount being perspired, and the cutaneous (inside the skin) blood flow. See Swift, “Transdermal Alcohol Measurement for Estimation of Blood Alcohol Concentration,” 24 Alcoholism: Clinical and Experimental Research 4, at 422 (April 2000).

These variables and the lack of understanding make the quantitative measurement of alcohol passing through the skin impossible. Consequently, blood alcohol content cannot be accurately estimated from perspired alcohol content the same way that it is estimated from measuring breath and to a lesser extent, urine. The SCRAM bracelet, therefore, can only be properly regarded as a screening tool to help establish continued abstinence. This position is well established in the scientific literature, and is accepted by AMS. See Brown, supra, at 539.

Nevertheless, while placed on the subject’s ankle, the device monitors the subject’s perspiration by taking quantitative measurements every hour. If alcohol is detected, the quantitative measurements are taken twice per hour. The obtained quantitative measurements are then converted from a perspiration alcohol level to a blood alcohol level. For this purpose, AMS uses the acronym “TAC”, meaning “transdermal” alcohol content. These TAC readings are communicated via a home-placed modem to a remote computer that is managed and hosted by AMS. The system uses a web-based application called “SCRAMnet.” AMS employees monitor and interpret the transferred data to determine if a drinking episode can be confirmed. These TAC readings are transferred between the bracelet and the modem via a 900 MHz radio signal.

The monitoring agency also tracks the wearer’s body temperature, as well as the distance of the device from the wearer’s skin. These variables are independently plotted onto a three-color graph. AMS provides this graph to the monitoring agency to substantiate their claim that a drinking event has been verified. AMS claims that the graph for a drinking episode can easily be distinguished from a graph that is the product of an interfering (non-ethanol) substance because TAC readings from a verified drinking episode are expected to gradually rise and fall off, while readings from an interfering substance are expected to rapidly peak then fall. Thus, it is assumed that a drinking episode will follow the typical absorption, distribution and elimination curve, while an interfering substance will not. If the wearer attempts to block the device from taking readings, the graph will include a flat-line that reflects the insertion of a blocking substance between the device and wearer’s skin. If this were to occur, the temperature readings would also be affected, and would also be reflected in the graph.


It has been AMS’s position that the SCRAM bracelet has never produced a false positive. This position was at least partially confirmed by a laboratory study funded by AMS. The research for this study was done through the University of Colorado, and involved both a laboratory group and a community group. The laboratory group included 24 individuals who were given known doses of alcohol. During testing, these individuals were apparently kept in the laboratory. For this group, the authors unequivocally stated that there were no transdermally-produced false positives. A second community group, which included 20 individuals, self-reported alcohol use, and were otherwise allowed to go about their daily activities. With this community group, there was less agreement between breath and transdermal readings, including instances where the transdermal readings and self-reported alcohol consumption did not match. However, upon a close reading, it appears that the authors were not willing to state unequivocally that there were no false positives for the community group, although the study does indicate that there were no false negatives. See Sakai, “Validity of Transdermal Alcohol Monitoring: Fixed and Self-Regulated Dosing,” 30 Alcoholism; Clinical and Experimental Research 1, at 26-33 (2006).

Perhaps the most significant potential limitation to the SCRAM technology is that the device uses a fuel cell to measure the TAC and fuel cells are known to be non-specific for beverage alcohol. For example, fuel cells can potentially respond to other alcohols that may be present in a person’s body, such as methyl-, isopropyl- and n-propyl alcohol. Fuel cells can also respond to acetaldehyde. See Garriott, Medical-Legal Aspects of Alcohol, at 197 (4th ed. 2003). This problem with non-specificity is particularly important with the SCRAM device because the measurements are taken above the skin, and this might allow environmental factors to be inadvertently measured by the device. Thus, it is at least theoretically possible for both endogenous as well as exogenous alcohol to produce false TAC readings.


Once a drinking episode has been confirmed by AMS, these findings are reported back to the local state agency, which is usually closely associated with the court where the offender’s case is pending. The court will then notify the offender. The type and time of notice may depend on the status of the case when the violation occurs. For example, if the offender is on bond, he or she may face a bond revocation hearing. Alternatively, if the allegation of alcohol use occurs post-conviction, the offender may face a revocation of probation. The result of an adverse finding for either violation may be lengthy incarceration. Where such violations are alleged, counsel should consider evaluating whether or not there has been a failure to provide the defendant with timely notice or perhaps a denial of the meaningful opportunity to be heard. Both are legitimate concerns because the “confirmation” process itself is not immediate. In practice, the total delay between drinking and notice of confirmation to the offender might be as much as several weeks.

Because of this delay, the ability to collect a potentially exculpatory independent breath or blood test at or near the time of the alleged drinking has long since passed. Thus, the offender will find him or herself in the unenviable position of having to prove a negative, that is, that they were not drinking, and they will have to do so without any ability to collect convincing evidence to support their denial.

A review of the applicable case law suggests that while this specific issue relative to the SCRAM bracelet has not been addressed at either the state or federal level, federal courts have resolved the more general right to obtain exculpatory evidence in favor of the accused. See Brady v. Maryland, 373 U.S. 83; 83 S.Ct. 1194; 10 L. Ed. 215 (1963).


Defending an allegation of alcohol use requires counsel to first obtain the graphs from the monitoring agency. The graphs will contain three curves, one each for the infrared signal (used to monitor distance from the skin), the subject’s temperature and the alleged TAC. These graphs should be accompanied by a linear numeric read-out of each individual TAC reading. Counsel must scrutinize these graphs to determine if in fact the “numbers” appear to reflect a typical blood alcohol curve, and whether or not any blocking episode coincides with the drinking. With respect to an analysis of the blocking aspect, bear in mind the delay associated with the TAC relative to the BAC. While it may appear at first that the blocking coincides with the drinking, upon closer inspection a different picture may emerge. This is because the infrared signal is in “real time,” while the TAC may actually be attenuated by as much as 120 minutes or more. See Swift, et al., “Studies on a Wearable, Electronic, Transdermal Alcohol Sensor,” 16 Alcoholism: Clinical and Experimental Research 4, at 721 (Aug. 1992).

Counsel should also obtain a detailed medical history, as well as detailed narrative of what the defendant was doing before, during, and after the alleged drinking episode. It should be determined whether or not the offender has any medical conditions or has experienced a chemical or radio frequency exposure that could cause a false positive. A viable defense might emerge if there is a correlation between such exposure and the alleged drinking.

If there appears to be legitimate support for your client’s contention that he or she was not drinking, counsel should request an evidentiary hearing.  A due process claim should also be evaluated based on the inherent inability of your client to obtain a potentially exculpatory independent test.