A judge who orders alcohol monitoring is not choosing a single tool. There are several, and they measure different things over different windows of time. A probation officer who understands the difference between a urine EtG screen, a PEth blood draw, a continuous transdermal monitor, and an ignition interlock can match the tool to the risk instead of defaulting to whatever the department has always used. This matters because each option answers a different question: did this person drink in the last day, did they drink heavily in the last few weeks, are they drinking right now, or can they get behind the wheel sober.
Why Courts Order Alcohol Monitoring
Alcohol monitoring shows up most often in DUI and DWI cases, but it is not limited to them. Family courts order it in custody disputes where drinking is a safety concern. Drug courts and other treatment courts build it into abstinence conditions. Probation departments use it as a compliance check between hearings. In many programs the requirement is layered: a person on probation for a repeat DUI may face urine screens at check-ins, a PEth draw at intake and periodically after, and an interlock requirement on any vehicle they drive. A closer look at how probation programs structure these requirements, testing frequency, sanctions, and reporting, is covered in how court ordered testing programs are structured.
EtG and EtS Urine Testing
Ethyl glucuronide (EtG) and ethyl sulfate (EtS) are direct metabolites of alcohol, meaning the body only produces them after alcohol is actually consumed, not from some indirect metabolic side effect. They are usually measured together in urine and can turn positive shortly after even low level exposure to alcohol. According to the SAMHSA biomarkers advisory hosted by the National Institute on Alcohol Abuse and Alcoholism, EtG and EtS can remain detectable in urine for one to two days after a single exposure, and the sensitivity of the test is high enough that it will pick up trace alcohol from sources that have nothing to do with drinking.
That sensitivity is the tradeoff. Hand sanitizer, mouthwash, certain cooking extracts, and other everyday products contain alcohol, and exposure to them can raise EtG and EtS levels enough to produce a positive result in someone who has not had a drink. The same advisory is explicit that biomarkers like EtG should not be used as the sole basis for a high stakes decision because of this false positive risk, and it recommends interpreting results alongside the person's history, product exposure, and, where possible, a second biomarker. A deeper comparison of how EtG stacks up against PEth on sensitivity, cost, and use case is available in PEth versus EtG for court and treatment programs.
PEth Blood Testing
Phosphatidylethanol (PEth) is also a direct biomarker, but it is drawn from blood rather than urine and it looks back much further. PEth forms only when alcohol is present, and the same NIAAA advisory notes it can persist in blood for as long as three weeks after just a few days of moderately heavy drinking, roughly four drinks a day. A 2023 systematic review published in PubMed Central found PEth's diagnostic specificity for alcohol exposure is close to 100 percent, since nothing else in the body forms it, though reported sensitivity and specificity ranges vary depending on the cutoff a lab uses.
Because of that longer window, PEth is a better fit when a court or treatment program wants to know whether someone has resumed regular drinking over the past several weeks rather than whether they had a drink yesterday. It requires a blood draw, which usually means a lab or clinical setting rather than a quick in office cup test, and it costs more per test than a urine EtG screen. Programs commonly use PEth at intake and at longer intervals, reserving urine EtG for frequent spot checks between draws.
SCRAM and Continuous Transdermal Alcohol Monitoring
Continuous transdermal monitors, often referred to by the brand-agnostic term SCRAM (secure continuous remote alcohol monitor), are worn as an ankle bracelet and sample perspiration through the skin at set intervals around the clock. Instead of a single point in time result, the device builds a continuous record and flags any reading consistent with drinking. A systematic review of wearable transdermal alcohol sensors published in PubMed Central found that transdermal readings correlate moderately to strongly with breath alcohol concentration in controlled studies, though the correlation strength varies by device and study design.
The same review flagged real limitations worth knowing before a court relies on the data alone. Transdermal readings lag behind actual blood alcohol, sometimes by an hour or more, because alcohol has to diffuse through the skin before the sensor picks it up. Environmental sources such as perfume or hand sanitizer applied near the device can occasionally trigger a false reading, similar to the exposure problem with EtG. And the review noted that most of the underlying research was done on healthy adult volunteers in short studies rather than the justice-involved or treatment populations the devices are actually used to monitor, which is a gap worth factoring into how much weight a single flagged event should carry.
Ignition Interlock Devices
An ignition interlock is a breath testing device wired into a vehicle's ignition system. The driver blows into it before the engine will start, and the device requires rolling retests at random intervals while the vehicle is running to prevent someone else from providing the initial sample. Interlocks are ordered as a condition of driving privileges, usually after a DUI conviction, and compliance is typically monitored jointly by the court and the state's licensing agency.
A five year evaluation of Michigan's DWI and sobriety court interlock program, published by the Michigan State Court Administrative Office, found that 97.0 percent of participants ordered to install an interlock actually complied, only 0.6 percent removed the device without authorization, and just 1.0 percent were caught tampering with it. The same report found that alcohol and drug use among interlock program participants was substantially lower than among a comparison group of standard probationers, and that interlock participants had a lower program failure rate, 11.4 percent, than is typical for DWI court populations generally. Those numbers make interlocks one of the more consistently effective tools in this category, though they only monitor alcohol at the moment someone tries to drive, not throughout the day.
Comparing the Four Options
| Method | Specimen | Typical Detection Window | What It Confirms | Main Limitation |
|---|---|---|---|---|
| EtG/EtS urine test | Urine | About 1 to 2 days after low level exposure, longer after heavier drinking | Recent alcohol exposure | Can be triggered by incidental alcohol exposure, not just drinking |
| PEth blood test | Blood | Up to about 3 weeks after several days of moderately heavy drinking | Sustained or repeated heavy drinking over weeks | Requires a blood draw, higher cost, slower turnaround |
| Continuous transdermal (SCRAM-type) | Perspiration through skin | Continuous, around the clock while worn | Drinking events over the monitoring period | Reading lag versus real time BAC, possible environmental interference |
| Ignition interlock | Breath | At the moment of vehicle startup and rolling retests | Sobriety at the point of driving | Only monitors while operating that specific vehicle |
Choosing the Right Option for a Program
None of these four is a universal answer. A drug court doing weekly check-ins often leans on urine EtG cups or dip cards because they are fast, inexpensive, and easy to administer at intake. A treatment program tracking whether a client has stayed sober over the course of a month is better served by PEth. A probation department supervising a high risk repeat offender may combine a continuous transdermal monitor with an interlock, so driving sobriety and general sobriety are both covered. Departments building or restocking a testing program can source EtG cups, dip cards, and related collection supplies through American Screening's drug and alcohol testing supplies, which is a practical starting point when a program needs to standardize what it hands out at intake.
Whatever combination a program lands on, the goal is matching the tool's window and confirmation power to the actual question being asked. A single EtG cup will not tell a family court judge whether a parent has been drinking steadily for a month, and a PEth draw will not tell a probation officer whether someone drove home intoxicated last night. Layering methods, rather than picking one and hoping it covers everything, is generally what produces defensible results.
Frequently asked questions
How long does alcohol stay detectable with an EtG urine test?
Typically one to two days after a single low level exposure, though heavier or repeated drinking can extend that window. The exact number depends on how much was consumed, hydration, and individual metabolism, which is why programs often use EtG for recent, rather than long-term, abstinence checks.
Can hand sanitizer or mouthwash cause a false positive EtG result?
Yes. EtG and EtS are highly sensitive tests, and products containing alcohol, including hand sanitizer, mouthwash, and some cosmetics or cleaning products, can raise levels enough to produce a positive result without any drinking. This is why regulators caution against using EtG alone for major decisions and recommend reviewing exposure history alongside the result.
Is PEth testing more reliable than EtG for court cases?
PEth and EtG answer different questions rather than one simply being better. PEth has very high specificity for alcohol exposure and covers a much longer window, which makes it useful for confirming sustained drinking patterns. EtG is faster and cheaper and better suited to catching recent use. Many programs use both rather than choosing one over the other.
Do ignition interlocks actually reduce repeat DUI offenses?
Evaluation data supports that they help while installed. A multi-year Michigan court evaluation found high compliance rates, low tampering, and lower alcohol and drug use among interlock program participants compared to a similar group of offenders without an interlock, along with a lower overall program failure rate.
Can someone get around a continuous transdermal alcohol monitor?
Tampering attempts happen, and monitoring programs generally include tamper alerts for exactly that reason. Research on these devices also shows a lag between actual blood alcohol levels and what the sensor reads, so isolated readings are usually reviewed in context rather than treated as an instant, real time result.
Related reading
This article is general information, not legal or medical advice. Alcohol testing methods, cutoff levels, and program requirements vary by jurisdiction and by court, so anyone building or complying with a court ordered monitoring plan should confirm the specific requirements with the court, probation department, or laboratory involved.
