Breathalyzer
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A breathalyzer (or breathalyser) is a device for estimating blood alcohol content (BAC) from a breath sample. "Breathalyzer" is the brand name of a model made by one manufacturer of these instruments (originally Smith and Wesson, later National Draeger), but has become a genericized trademark for all such instruments. Intoxilyzer, Intoximeter, Alcotest, Alcosensor and Datamaster are the other most common brand names in use today.
Though technologies for detecting alcohol vary, it's widely accepted that Dr. Robert Borkenstein (1912-2002), a captain with the Indiana State Police and later a professor of Indiana University at Bloomington, is regarded as the first to create a device that measures a subject's alcohol level based on a breath sample. In 1954, Borkenstein invented his breathalyzer, which used chemical oxidation and photometry to determine alcohol concentration. The invention of the breathalyzer provided law enforcement with a non-invasive test with immediate result reporting that can be used to determine an individual's level of intoxication. The various versions of the Breathalyzer were made by Smith and Wesson, the gun manufacturer, until the sale of the line to the German company National Draeger.
Breath analyzers don't directly measure blood alcohol content or concentration, which requires the analysis of a blood sample. Instead, they estimate BAC indirectly by measuring the amount of alcohol in one's breath. Three technologies are in use: evidentiary machines, used by policeforces, which generally utilize infrared spectrophotometer technology; less accurate hand-held electrochemical fuel cell-based instruments, used by officers in the field and commonly called PBT (preliminary breath test) or PAS (preliminary alcohol screening); and semiconductor oxide based testers, cheapest and least reliable but becoming increasingly popular for personal and professional testing applications.
The breath alcohol reading is used in criminal prosecutions in two ways. Unless the suspect refuses to submit to chemical testing, he will be charged with a violation of the so-called illegal per se law: it is a misdemeanor throughout the United States to drive a vehicle with a BAC of .08% or higher (the forbidden level is .02% in most states for drivers under 21). The breathalyzer reading will be offered as evidence of that crime, although the issue is what the BAC was at the time of driving rather than at the time of the test. The suspect will also be charged with driving under the influence of alcohol (sometimes referred to as driving or operating while intoxicated). While BAC tests are not necessary to prove a defendant was under the influence, laws in most states require the jury to presume that he was under the influence if his BAC was over .08% when driving. This is a rebuttable presumption, however: the jury can disregard the test if they find it unreliable or if other evidence establishes a reasonable doubt.
Some states don't permit data or "readings" from hand-held devices to be presented as evidence in court. They are generally admissible, if at all, only to show the presence of alcohol or as a field sobriety test to help determine probable cause to arrest. South Dakota does not permit data from any type or size breath tester but relies entirely on blood tests to ensure accuracy.
Common problems
A major problem with some machines is that they not only identify the ethyl alcohol (or ethanol) found in alcohol beverages, but also other substances similar in molecular structure. Those machines identify any compound containing the methyl group structure. Over one hundred compounds can be found in the human breath at any one time and 70 to 80 percent of them contain methyl group structure and will be incorrectly detected as ethyl alcohol. Importantly, the more different ethyl group substances the machine detects, the higher the false BAC estimate will be.
The National Highway Traffic Safety Administration (NHTSA) has found that dieters and diabetics can have acetone levels hundreds and even thousand of times higher than those in others. Acetone is one of the many substances that can be falsely identified as ethyl alcohol by some breath machines.
Substances in the environment can also lead to false BAC readings. For example, an alcohol-free subject was asked to apply a pint of contact cement to a piece of plywood and then to apply a gallon of oil-base paint to a wall. The total activity lasted about an hour. Twenty minutes later the subject was tested on an Intoxilyzer, which registered a BAC of .12 percent. This level is 50% higher than a BAC of .08, which constitutes legal intoxication.
Any number of other products found in the environment can cause erroneous BAC results. These include compounds found in lacquers, paint removers, celluloid, gasoline, and cleaning fluids. Other common things that can cause false BAC levels are alcohol, blood or vomit in the subject's mouth, electrical interference from cell phones and police radios, tobacco smoke, dirt, and moisture.
Breath testers can be very sensitive to temperature and will give false readings if not adjusted or recalibrated to account for ambient or surrounding air temperatures. The temperature of the subject is also very important. Each one Fahrenheit degree of body temperature above normal will cause a substantial elevation (about 8%) in apparent BAC.
Breath testing machines assume a 2100-to-1 ratio in converting alcohol measured in the breath to estimates of alcohol in the blood. However, this "partition ratio" varies from 1300:1 to 3000:1 or more among individuals and within a given individual over time. Assuming a true (and legal) blood-alcohol concentration of .07%, for example, a person with a partition ratio of 1500:1 would have a breath test reading of .10% -- over the legal limit.
Breathing pattern can also significantly affect breath test results. One study found that the BAC readings of subjects decreased 11 to 14% after running up one flight of stairs and 22-25% after doing so twice. Another study found a 15% decrease in BAC readings after vigorous exercise or hyperventilation. Hyperventilation for 20 seconds has been shown to lower the reading by approximately 10%. On the other hand, holding your breath for 30 seconds can increase the breath test result by about 15%.
Some breath analysis machines assume a hematocrit (cell volume of blood) of 47%. However, hematocrit values range from 42 to 52% in men and from 37 to 47% in women. A person with a lower hematocrit will have a falsely high BAC reading.
Failure of law enforcement officers to use the devices properly or of administrators to have the machines properly maintained and re-calibrated as required are additional sources of error.
Research indicates that breath tests can vary at least 15% from actual blood alcohol concentration. An estimated 23% of individuals tested will have a BAC reading higher than their true BAC.
Police in Victoria, Australia use breathalyzers that give a 20 per cent tolerance on readings. Noel Ashby, Victoria Police Assistant Commissioner (Traffic & Transport) claims that this tolerance is to allow for different body types.Jane Holroyd, [Breathalyser's 20 per cent tolerance defended], Sydney Morning Herald, 16 May, 2006
Principles of Chemical Testing
The "Breathalyzer" brand breath-testing device operates by using photocells to analyze the colour change of an oxidation-reduction reaction. A breath sample is bubbled through an aqueous solution of sulfuric acid, potassium dichromate, and silver nitrate. The silver nitrate acts as a catalyst, allowing the alcohol to be oxidized at an appreciable rate. The requisite acidic condition needed for the reaction might also be provided by the sulfuric acid. In solution, ethanol reacts with the potassium dichromate, reducing the dichromate ion to the chromium (III) ion. This reduction results in a change of the solution's colour from red-orange to green. The reacted solution is compared to a vial of nonreacted solution by a photocell, which creates an electric current proportional to the degree of the colour change; this current moves the needle that indicates BAC.
Like other methods, the "Breathalyzer" chemical analysis is somewhat prone to false readings; compounds which have compositions similar to ethanol could also act as reducing agents, creating the necessary colour change to indicate increased BAC.
Myths
A common myth is that breath testers can be "fooled" (that is, made to generate estimates making one's blood alcohol content appear lower) by using certain substances. An episode of the Discovery Channel's MythBusters tested substances usually recommended in this practice -- including breath mints, mouthwash, and onion -- and found them to be ineffective. Adding an odor to mask the smell of alcohol might fool a person, but does not change the actual alcohol concentration in the body or on the breath.On the other hand, products such as mouthwash or breath spray can "fool" breath machines by significantly raising test results. Listerine, for example, contains 27% alcohol; because the breath machine will assume the alcohol is coming from alcohol in the blood diffusing into the lung rather than directly from the mouth, it will apply a "partition ratio" of 2100:1 in computing blood alcohol concentration -- resulting in a false high test reading.
This was clearly illustrated in a study conducted with Listerine mouthwash on a breath machine and reported in an article entitled "Field Sobriety Testing: Intoxilyzers and Listerine Antiseptic", published in the July 1985 issue of The Police Chief (page 70). Seven individuals were tested at a police station, with readings of .00%. Each then rinsed his mouth with 20 milliliters of Listerine mouthwash for 30 seconds in accordance with directions on the label. All seven were then tested on the machine at intervals of one, three, five and ten minutes.
The results indicated an average reading of .43% blood-alcohol concentration -- indicating a level that, if accurate, approaches lethal proportions. After three minutes, the average level was still .20%, despite the absence of any alcohol in the system. Even after five minutes, the average level was .11% -- well over the legal limit.
In another study, reported in 8(22) Drinking/Driving Law Letter 1, a scientist tested the effects of Binaca breath spray on an Intoxilyzer 5000. He performed 23 tests with subjects who sprayed their throats, and obtained readings as high as .81% -- far beyond lethal levels. The scientist also noted that the effects of the spray did not fall below detectable levels until after 18 minutes.
References
- Hlastala, M. Physiological errors associated with alcohol breath tests . The Champion, 1985, 9,(6).
- Pariser, J. L. In vino Veritas: the truth about blood alcohol presumption in state drunk driving laws. New York Law Review, 1989, 64(1), 141-181.
- Peach, R. J. Who tests the DUI test? Defense can't; New Jersey won't let lawyers inspect new breath tests. The National Law Journal, 2000, 23(6), A4.
- Rosenblum. E. Breathlayzer machines are faulted once more. New Jersey Law Journal, 1988, 122(23), 5.
- Sargeant, G. Breathalyzer accuracy challenged. Trial, 1989, 25(12), 22.
- Taylor, L. Drunk Driving Defense. New York: Aspen Law and Business, 6th edition, 2005.
- Based on information in [Breathalyzer.net Frequently Asked Questions]
- Based on information in [Alcohol: Problems and Solutions]
- [Breath Tester Accuracy]
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