What I Learned in Ohio That Most UK Lawyers Don’t Know
In 2007, at the very early stages of my career in motoring law, I made a decision that still sets me apart from most other solicitors in the field: I travelled to Ohio, USA, to undertake a specialist training course on the Camic Datamaster breathalyser. The course was led by the very manufacturers and engineers who built and developed the device.
This wasn’t just about ticking a box on a CPD record. It was about one thing: understanding. Understanding how breath test machines really work. Understanding how they can fail. And most importantly, understanding how to defend my clients properly in drink driving cases when these machines are at the centre of a prosecution.
At the time, there was no equivalent training available in the UK. The inner workings of these devices were (and still are) cloaked in a level of secrecy. Whether it’s a result of police policy, manufacturer agreements, or an overarching desire to present the machines as infallible, it is notoriously difficult for defence lawyers to access technical information in this country.
But true to my tenacious approach to my clients’ cases, I wasn’t willing to accept that and I embarked on a trip to USA to try and uncover the workings and some of the known issues with the device.
What is the Camic Datamaster Breath Test Machine?
The Camic Datamaster is one of three evidential breath test machines currently approved by the Home Office for use in UK police stations. It uses infrared spectroscopy to measure the level of alcohol in a person’s breath. Here’s how it works:
- The subject blows into the machine.
- Their breath passes through a chamber where infrared light is projected.
- Alcohol molecules absorb specific wavelengths of this light.
- The device measures how much light is absorbed and converts that into a breath alcohol concentration (BrAC).
The machine typically takes two breath samples a few minutes apart. These samples must be within a tight range to ensure accuracy. The Camic Datamaster also performs internal checks before, during, and after the test to ensure the environment and equipment are free from contamination.
What Can Go Wrong With a Breath Test?
Despite the sleek design and scientific principles, these machines are not foolproof. Some of the issues I explored during my Ohio training, and have seen countless times in practice, include:
- Mouth alcohol: Residual alcohol from recent drinks, mouthwash, or gastric reflux can lead to falsely elevated results.
- Sample flow issues: People with asthma, COPD, or other breathing difficulties may struggle to produce a valid sample, resulting in test errors or wrongful accusations of refusal.
- Calibration errors: The machine must be properly calibrated and maintained. If it isn’t, readings may be skewed.
- Operator error: Although largely automated, human oversight is still required. Missteps in procedure can affect the outcome.
These are not just theoretical concerns. They are real-world issues that we at Geoffrey Miller Solicitors have challenged successfully time and again.
Other Machines Used for Breath Tests in the UK
Alongside the Camic Datamaster, two other machines are currently type-approved for use in the UK:
1. Lion Intoxilyzer 6000UK
This device also uses infrared technology to detect ethanol in a person’s breath. The machine requires a steady, deep-lung exhalation. If the breath flow is irregular or too short, the machine may reject the sample or falsely interpret it as non-compliance.
Known issues:
- Overly sensitive flow detection
- Susceptibility to sensor or software faults
- Rejecting valid attempts due to volume/pressure thresholds
2. Intoximeter EC/IR
This machine uses a dual system combining infrared and fuel cell technology. The IR sensor confirms that the breath sample is valid and comes from deep within the lungs. The fuel cell then provides a chemical measurement of alcohol content.
Known issues:
- High blank or purge failures
- False positives from mouth alcohol
- Calibration drift if not serviced regularly
- Rejection of samples from individuals with low lung capacity
All of these devices require precise operation, controlled conditions, and a subject capable of performing the test correctly. Unfortunately, many of our clients have found themselves wrongly accused because of failings in one or more of these areas.
My Perspective as a Solicitor with Specialist Drink Driving Knowledge
While I am not a forensic scientist, I am a solicitor who has worked exclusively in motoring law for over two decades. And I can confidently say that my technical insight into the functionality of breath testing machines places me at the forefront of drink driving defence in the UK.
Most solicitors and even some barristers take breath test results at face value. But my team and I do not. I know what can go wrong, what should be tested, and when to call in a forensic expert.
At Geoffrey Miller Solicitors, we apply this insight rigorously. From 1 January 2021 to 31 December 2024, we defended 184 breath drink driving cases and won 157 of them. That’s a 85% success rate. In 2025 so far, we achieved a 100% success rate in our breath drink driving defended cases.
Why We Go the Extra Mile
That trip to Ohio in 2007 wasn’t a box-ticking exercise. It was an investment in technical knowledge, undertaken at a time when such insight was hard to come by in the UK legal world. It set the tone for everything we do at Geoffrey Miller Solicitors.
I even came across some old photos of the trip and the breath test I did during training along with all the US police officers’ cards on the wall! I think I was a bit of a strange novelty for the trainers but they certainly helped me to understand the issues that looking back I have to credit as being a crucial part of the foundation of my firm’s success.
If you’re facing a drink driving charge, or you’ve been accused of failing to provide a specimen, don’t assume the machine is right just because the police say it is. These devices are powerful, but they are not perfect. And when your licence, livelihood, and liberty are at stake, you need a team who understands both the law and the science.
Contact Geoffrey Miller Solicitors today for expert legal advice from a firm that knows breath testing inside and out.
Blog Written by Jeanette Miller – Drink Driving Solicitor
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