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Understanding the Limitations of Police Breathalysers

Breathalysers are a crucial tool for detecting alcohol consumption and preventing people from driving whilst under the influence. However, it is a common misconception that police breathalysers are infallible devices that can accurately measure the blood alcohol content of anyone who blows into them. It is important to recognise that there are certain situations in which some individuals may be unable to use police breathalysers effectively.

Under the 1988 Road Traffic Act, individuals who are unable to complete a breathalyser test are subject to automatic charges for Failure to Provide, an offence which can carry severe repercussions including driving disqualifications, up to six months imprisonment, and an unlimited fine. Data suggests approximately 4,000 people are prosecuted each year in the UK for Failure to Provide, but some of these could have been miscarriages of justice given many have legitimate reasons why they cannot use existing breathalysers.

Supportive research

Research carried out by the University of Sheffield earlier this year found that many people have physical characteristics that make them unable to comply with breathalyser tests. The study, which involved the analysis of 280,000 participants in the UK Biobank who underwent lung capacity tests, uncovered that a ‘significant minority’ lacked the necessary lung strength or capacity to produce a valid sample. This trend is especially notable among older individuals, women, smokers, and those of shorter stature.

  • Age
    When it comes to age, the issue lies in the impact of ageing on the lungs, chest, and diaphragm and the subsequent loss of tissue elasticity. The risk of not being able to provide a sample roughly doubles with each decade from the 40s to the 60s. When comparing individuals in their 40s with those in their 70s, the risk increases tenfold for men and sixfold for women. There is also a correlation between age and stature, with shorter, elderly individuals being the least likely to provide a sample, especially if they are female
  • Stature
    Up to one in 38 men and one in 26 women of smaller stature may face physiological limitations in providing an evidential breath sample. This challenge becomes more pronounced with advancing age, and the risk is doubled for regular smokers. Although variations exist between individuals of similar size, in general terms, the bigger you are, the bigger your lung capacity tends to be.
  • Gender
    The recent data suggests that, overall, nearly four times as many females may be unable to provide an evidential breath sample compared to males, although this difference diminishes with age. Gender remains a significant factor when considering age, stature, or smoking status on a person’s ability to submit a breathalyser reading, with women facing a higher risk than men in all examined circumstances.

Additional Factors

  • Medical Conditions
    Anyone suffering from respiratory conditions such as asthma or chronic obstructive pulmonary disease (COPD) may struggle to produce a sufficient breath sample for the breathalyser to analyse. Similarly, individuals with temporary conditions, such as a sore throat or impacts from recent oral surgery, may also encounter difficulties in providing a suitable breath sample.
  • Environmental Impacts
    External factors, such as extreme cold weather, can impact the functionality of police breathalysers and affect the ability of individuals to produce an adequate breath sample, while strong winds or high altitudes may also interfere with the accuracy of breathalyser readings.

Police officers must be aware of these limitations so they can exercise discretion when administering breathalyser tests. Individuals who cannot provide a suitable breath sample due to physical, medical, or other factors should be offered alternative methods of testing, such as blood or urine tests, to ensure a fair and accurate assessment of their blood alcohol content. This approach will reduce incorrect convictions and help promote trust and cooperation between the police and the public.

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