Breathalyzer
[4] Also in 1927, a Chicago chemist, William Duncan McNally, invented a breathalyzer in which the breath moving through chemicals in water would change color.
[5] In December 1927, in a case in Marlborough, England, Dr. Gorsky, a police surgeon, asked a suspect to inflate a football bladder with his breath.
[6] In 1931 the first practical roadside breath-testing device was the drunkometer developed by Rolla Neil Harger of the Indiana University School of Medicine.
The invention of the Breathalyzer provided law enforcement with a quick and portable test to determine an individual's intoxication level via breath analysis.
[9] In 1979, Lion Laboratories' version of the breathalyser, known as the Alcolyser and incorporating crystal-filled tubes that changed colour above a certain level of alcohol in the breath, was approved for police use.
[10] These later models used a fuel cell alcohol sensor rather than crystals, providing a more reliable curbside test and removing the need for blood or urine samples to be taken at a police station.
In 1991, Lion Laboratories was sold to the American company MPD, Inc.[8] There are a variety of mechanisms used in breathalyzers, for example oxidation with potassium permanganate, or infrared spectroscopy.
The electric current produced by this reaction is measured by a microcontroller, and displayed as an approximation of overall blood alcohol content (BAC) by the Alcosensor.
[citation needed] There are two ways of calibrating a precision fuel cell breath analyzer, the wet-bath and the dry-gas methods.
Some semiconductor models are designed specifically to allow the sensor module to be replaced without the need to send the unit to a calibration lab.
For example, the National Highway Traffic Safety Administration has found that dieters and diabetics may have acetone levels hundreds or even thousands of times higher than those in others.
During the absorptive phase, the concentration of alcohol throughout the body changes unpredictably, as it is affected by gastrointestinal physiology such as irregular contraction patterns.
Assuming a blood-alcohol concentration of 0.07%, for example, a person could have a partition ratio of 1500:1 and a breath test reading of 0.10 g/2100 mL, over the legal limit in some jurisdictions.
[17] Other false positives of high BrAC and also blood reading are related to patients with proteinuria and hematuria, due to kidney metabolization and failure.
[20] This brings up the question of what is meant by reporting BrAC as a single number; is it the "deep-lung air", the highest possible reading obtainable by the subject's full exhalation?
[22] The Supreme Court of California determined that the BrAC is defined as the alcohol concentration of the last part of the subject’s expired breath.
Recent use of mouthwash or breath fresheners can also skew results upward, as they can contain fairly high levels of alcohol.
There are a number of substances or techniques that can supposedly "fool" a breath analyzer (i.e., generate a lower blood alcohol content).
[29] Other substances that might reduce the BrAC reading include a bag of activated charcoal concealed in the mouth (to absorb alcohol vapor), an oxidizing gas (such as N2O, Cl2, O3, etc.)
All breath alcohol testers used by law enforcement in the United States of America must be approved by the Department of Transportation's National Highway Traffic Safety Administration.
In per se jurisdictions such as the UK, it is automatically illegal to drive a vehicle with a sufficiently high breath alcohol concentration (BrAC).
In other states, such as California and New Jersey, the statute remains tied to BAC, but the BrAC results of certain machines have been judicially deemed presumptively accurate substitutes for blood testing when used as directed.
[40][41] While BrAC tests are not necessary to prove a defendant was under the influence, laws in these states create a rebuttable presumption, which means it is presumed that the driver was intoxicated given a high BrAC reading, but that presumption can be rebutted if a jury finds it unreliable or if other evidence establishes a reasonable doubt as to whether the person actually drove with a breath or blood alcohol level of 0.08% or greater.
One exception to criminal prosecution is the state of Wisconsin, where a first time drunk driving offense is normally a civil ordinance violation.
The NSC has acknowledged that more recent research shows the actual relationship is most probably higher than 2100:1 and closer to 2300:1, but opines that this difference is of minimal practical significance in law enforcement.
Noel Ashby, former Victoria Police Assistant Commissioner (Traffic & Transport), claims that this tolerance is to allow for different body types.
[46] The US National Highway Traffic Safety Administration maintains a Conforming Products List of breath alcohol devices approved for preliminary screening use.
This closely relates to absorptive stage intoxication (or bolus drinking), except that the consumption of alcohol also occurred after driving.
[55] South Africa is more straightforward, with a separate penalty applied for consumption "After An Accident" until reported to the police and if so required, has been medically examined.
The prosecution typically provides an estimated alcohol concentration at the time of driving utilizing retrograde extrapolation, presented by expert opinion.
