Continuous Alcohol Monitoring:
A Forensic and Legal Examination of an Imperfect System
Counterpoint Volume 9: Issue 2 - Article 1 (June 2025)
An article in the Foundational Skills II-X Module
Jan Semenoff, BA, EMA
Forensic Criminalist
In recent years, Continuous Alcohol Monitoring (CAM) has become a mainstay in criminal justice supervision, serving as a condition of pre-trial release, probation, or diversion for individuals with alcohol-related offences and family matter concerns. And, as a matter of public value, these systems promise 24/7 oversight, an alternative to incarceration, and greater accountability. But, behind their scientific veneer lies a complex reality: the data they generate is not always reliable, with the consequences of misinterpretation severe. Therefore, understanding the limitations of the technology, and how to create a positive and successful environment for your client - is imperative.
This article synthesizes key findings from technical literature, forensic practice, and the MyCAMprogram educational initiative to provide defense counsel with a comprehensive overview of CAM. It explores how these technologies work, the legal and scientific challenges they present, and the strategies attorneys can use to safeguard their clients.
Overview of CAM Technology
CAM devices include transdermal ankle monitors, ignition interlock devices (IIDs), and handheld breath testers. Each operates on different principles:
- Transdermal Monitors (e.g., ankle bracelets) detect alcohol vapor emitted through the skin. They typically record data every 30 minutes.
- Ignition Interlocks require a breath test before a vehicle can start. They use fuel cell sensors and capture photos or video for identity verification.
- Handheld Devices may prompt users at random times to submit a breath sample, often with location tracking and photo or video confirmation.
These technologies are often used in parallel with court mandates and monitoring agency oversight, with results delivered through centralized databases or non-compliance reports.
Where and Why CAM is Used
CAM is used extensively across the U.S. and in countries such as Canada, the UK, and Australia. Applications include:
- Criminal Law: DUI cases, repeat alcohol offences, probation and parole supervision.
- Family Law: Custody disputes, domestic violence cases, and supervised parenting time.
- Sobriety and Treatment Courts: Rehabilitation-focused models integrating CAM into a broader support plan.
Courts see CAM as a tool for accountability. But the perception of objectivity often outweighs a critical examination of the science. We need to examine why?
False Positives and Environmental Interference
Despite manufacturer claims, CAM devices are not immune to contamination or interference:
- Transdermal sensors can and do detect alcohol from topical exposures such as hand sanitizers, colognes, or cleaning products.
- Fuel cell breath testers can react to compounds like isopropanol, acetone, or methyl ethyl ketone. These substances are naturally produced during ketosis, fasting, or diabetic episodes, and are common in many industrial environments.
Studies confirm that even strict algorithmic filters cannot eliminate all false positives. These filters, while conservative, may also mask real data inconsistencies.
For attorneys, this means that positive readings should never be taken at face value. Without considering context, the data may be misleading.
Data Interpretation Challenges
Understanding how to interpret CAM data is essential:
- TAC vs. BAC: Transdermal readings do not measure blood alcohol concentration directly. They lag behind BAC changes and are affected by skin properties, sweating, hydration, and individual metabolism.
- Mathematical modeling: Algorithms convert TAC to reportable events, but thresholds can vary across jurisdictions.
- Physiological differences: Gender, body mass, and health conditions can significantly affect sensor readings.
Attorneys must advocate that these readings are just one piece of the puzzle - not a standalone proof of consumption, intoxication, or intent.
Calibration and Reliability Concerns
All CAM devices rely on fuel cell technology, which requires regular calibration. Failures in this process are common and can go unnoticed:
- Devices may drift over time.
- Calibration logs are often unavailable or incomplete.
- Malfunctions - like sensor faults, software errors, or battery failure - can trigger spurious results or gaps in monitoring.
Requesting and reviewing calibration and maintenance logs is a vital part of any defense strategy. Lack of documentation may be grounds for excluding or challenging CAM evidence.
Strategic Defense Considerations
Defending a client in a CAM program requires both proactive and reactive measures:
- Investigate the data: Demand access to the raw dataset, not just summary reports. Look for patterns, gaps, or anomalies. Focus on elimination rates.
- Document exposures: Encourage clients to keep daily logs of any use of alcohol-based products, medical symptoms, or environmental conditions.
- Challenge causation: Use expert testimony to explain how false positives or lag effects may have occurred.
- Scrutinize device performance: Cross-examine on calibration records, software updates, and known limitations.
- Distinguish consumption from exposure: Courts must be reminded that detection is not proof of volitional drinking.
In essence, attorneys should treat CAM readings the way they treat forensic breath or blood tests - with skepticism, scrutiny, and scientific challenge.
COMING FALL 2025:
The Role of Participant Education
One overlooked factor in CAM success is user education. Most participants are not told:
- How their devices function
- What substances can cause false positives
- How to respond to unexpected alerts
- How to record their own corroborating data
The MyCAMprogram was developed to fill this gap. Created by forensic experts, it teaches participants how to protect themselves with accurate record keeping, awareness of medical conditions, and safe product substitution. While not a substitute for legal counsel or medical advice, it empowers clients and provides supporting documentation that can aid in court.
Educated clients are less likely to generate false positives - and better equipped to respond if one occurs.
COMING FALL 2025 |
Final Considerations for Legal Professionals
CAM is often perceived by courts as an impartial watchdog. But its evidentiary value depends entirely on context, calibration, and interpretation. Legal professionals must:
- Stay current with the science
- Understand each device's design and limitations
- Educate clients about compliance and documentation
- Resist over reliance on vendor-produced summaries
As CAM programs grow, criminal defense and family law practitioners will increasingly be called upon to challenge their results. Doing so effectively requires more than cross-examination. It requires fluency in forensic alcohol testing, a strong evidentiary foundation, and a willingness to confront technology with science.
In the courtroom, as in the lab, precision matters. So does context. Continuous Alcohol Monitoring may track molecules - but it’s up to the legal system to ensure it doesn’t trample rights along the way.
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