The are three variables that must considered in evaluating the validity of any breath test result: (1) the machine on which the test was performed, (2) the individual being tested, and (3) the way in which the test was performed.

The Intoxilyzer 5000 is the machine upon which all breath tests are currently performed in Georgia. The Intoxilyzer 5000 works on the basic premise that a small, yet measurable portion, of alcohol is eliminated through the breath, and the machine attempts to extrapolate the concentration of alcohol in a person’s blood based on the concentration of alcohol in a person’s breath. Ultimately, it is critical to understand the concentration of alcohol in a person’s blood, rather than their breath, because it is alcohol in the blood that allegedly “impairs” the person by affecting their neurological functioning.

Alcohol typically enters the body through oral ingestion of a beverage containing ethyl alcohol. Alcohol enters the bloodstream through the stomach and small intestine by simple diffusion.

Blood transports the alcohol, which is infinitely water soluble, to the bodily tissues. Veins carry the blood to and through the lungs where the blood becomes oxygenated. Arteries then carry the oxygen-rich blood to the brain and the rest of the body.

Lung tissue is made of air pockets, or alveoli, surrounded by blood-rich membranes. A fraction of the alcohol circulating in the blood crosses the membranes and evaporates into the alveoli. During exhalation, air is forced out of the alveoli and ultimately emerges from the lungs into the breath.

During exhalation, air first emerges from the mouth/nasal area, then the throat and upper airway, then the lungs. The highest alcohol concentration in the lungs is found in the deepest portion of the lungs, where the air is in its closest proximity to the blood. When a person exhales completely, the “deep” lung air (also known as the “end expiratory” air) leaves the lungs last. If one were to monitor breath alcohol levels while a person exhaled , the measured level would start at a very low level and rise until it reached a peak or “plateau” as deep lung air is exhaled.

So, you may be wondering “even if the Intoxilyzer 5000 can measure the amount of alcohol in a breath sample, what does that have to do with the amount of alcohol that is allegedly in my blood?” Breath alcohol analysis is based on the theory that the distribution of alcohol between circulating blood and deep lung air obeys Henry’s Law.

Henry’s Law describes the mechanism of exchange in the lungs, which is influenced by physiological factors. Henry’s law purportedly explains the volume of alcohol in a simulator’s vapor. Henry’s Law states that in a closed system, at any given temperature, the concentration of a volatile substance in the air above a fluid is proportional to the concentration of the volatile substance in the fluid.

Under Henry’s Law, if a closed bottle partially filled with a solution of alcohol and water is shaken, some of the alcohol will transfer from the solution and mix with the air in the bottle. This air/alcohol mixture will reach a certain concentration and will stop. This point is known as equilibrium. At equilibrium, for any given temperature and pressure, there will be a definite ratio between the amount of alcohol in the air and in the water. The higher the temperature, the more alcohol will be in the air. Conversely, the lower the temperature, the less alcohol will be in the air.

If the Intoxilyzer 5000 is to provide an accurate result, alcohol must obey Henry’s Law and there must be a distributive equilibrium. Therefore, at a given temperature, a constant ratio must exist between the concentration of alcohol in the blood and in deep lung air. According to the State, the average temperature at which the breath leaves the mouth is 34 degrees celsius. Therefore, the ratio between the concentration of alcohol in blood and deep lung air with it is on equilibrium must be determined at 34 degrees celsius. According to the state, this ratio is 2100:1, which means that 2100 ml of deep lung air contains the same quantity of alcohol as 1 ml of arterial blood.

There are numerous critics of this application of Henry’s Law. Experts examining this application of Henry’s Law states: The comparison being made is that the lungs are like the bottle, the blood in the lungs are like the liquid in the bottle, and the breath is like the gas phase above the liquid. Unfortunately, Henry’s Law does not apply in the lungs. In order for Henry’s Law to apply, three conditions must be met. One, the solution must be kept at a known, constant temperature. The lung temperature is never known, and the temperature is always changing. And three, the pressure must be kept constant. The lungs are always changing pressure, decreasing pressure to inhale and increasing pressure to exhale. Without all three conditions present, it is not possible for equilibrium to occur, and Henry’s Law does not apply.

The Intoxilyzer Model 5000 uses infrared (IR) light and five ethanol-specific IR filters to identify the ethyl alcohol molecule and to determine the percent of alcohol in a breath sample. These instruments utilize an analytical process known as infrared spectroscopy (IR).

The electromagnetic spectrum is a series of wave energies that begin far below radio waves and extends to cosmic waves. The visible light spectrum is a narrow band within the electromagnetic spectrum. Visible light, those frequencies detected by the human eye, contain all colors of the rainbow or those colors seen when passing white light through a prism. Not all light is visible to the human eye, particularly ultraviolet (UV) and infrared (IR).

Historically, infrared light has been used t identify chemical compounds. When infrared light is passed through a substance, some of the infrared light (energy) will be absorbed, Absorption occurs at different wavelengths and is dependent upon the molecular structure of the compound being tested. The molecules of any compound are composed of individual and uniquely arranged atoms. Each substance, therefore, will have a unique infrared pattern or spectrogram.

This absorption of light can be explained by the Beer-Lambert Law. Which states: “If a light is directed through a container, the amount of light detected on the other side of the container is decreased by any substances in the container in proportion to their absorption coefficients and concentrations, and is also decreased in proportion to the distance across the container.”

The Beer-Lambert Law of Absorption provides the theoretical basis for IR breath testing. Molecules absorb electromagnetic radiation at certain specific, unique wavelengths. Thus, it may be said that each molecule has its own “infrared fingerprint.” Ethyl alcohol absorbs radiation at wavelengths of approximately 3.00, 3.39, 7.25, 9.18, 9.50 and 11.5 microns. No other compound absorbs radiation at all of those wavelengths exclusively.

Infrared instruments measure energy entering a vapor-filled cavity or sample chamber inside the instrument. When the IR energy beam emerges from the sample chamber, the instrument measures an energy loss in the affected IR wavelength regions if alcohol is present. The more alcohol the sample contains, the greater the degree of absorption and the more IR energy loss.

 
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