San Diego DUI Attorney Defense Information - How reliable are those breath tests?

How reliable are those breath tests?

There are many faults with the way a breath testing machine analyses the air that is introduced to it. These tests can be very unreliable and susceptible to attack by a lawyer who understands the weakness of a "Breathalyzer".

One of the major defects in many methods of blood-alcohol analysis is the failure to identify ethanol (also referred to as ethyl alcohol) to the exclusion of all other chemical compounds. To use the terminology of scientists, such methods are not specific for ethanol: They will detect other compounds as well, identifying any of them as "ethanol." Thus a client with other compounds in his blood or breath may have a high "blood-alcohol" reading with little or no ethanol in his body.

This problem of nonspecificity is most noticeable in the use of infrared breath analyzing instruments (the most popular type of breath testing machines used today). Yet they are particularly susceptible to giving false readings due to nonspecificity. The technical reason for this lack of specificity is that most breath machines are not designed to detect the molecule of ethyl alcohol (ethanol), but rather only a part of that molecule—the methyl group. In other words, it is the methyl group in the ethyl alcohol compound that is absorbing the infrared light, resulting in the eventual blood-alcohol reading. Thus the machine will "detect" any chemical compound and identify it as ethyl alcohol if it contains a methyl group compound within its molecular structure. The "Breathalyzer" assumes that the methyl group is a part of an ethyl alcohol compound.

The simple fact is that there are numerous compounds that contain the methyl group.

Isopropyl Alcohol
Propane
Butane
Propylene
Methane
Ethane
Ethyl chloride
Acetic Acid
Butadiene
Dimethylether
Dimethylamine
Dimethylhydrazine

Acetone and acetaldehyde, interestingly, can be found on the human breath. In fact, recent studies have found that over one hundred chemical compounds can be found on the breath at any given moment in time. More important, approximately 70 to 80 percent of these compounds contain methyl groups. And the infrared breath machine will detect each of these as "ethyl alcohol".
To make matters worse, the machine detects alcohol through "additive absorption." In other words, the more methyl groups the instrument detects by their absorbing the infrared energy, the higher will be the blood-alcohol reading. Thus all of the non-alcoholic compounds on the breath will have a cumulative effect — that is, the errors will be added one on top of another.

How prevalent are chemicals in the breath that can register on breath analyzing machines? Here are some common things that can give falsely high readings:

Untreated Diabetics
Persons on a Weight Reduction Diet
Fasting
Long-term smokers are more likely to have higher blood-alcohol readings due to a greater amount of acetaldehyde in the lungs.
Alcoholics can have 5 to 55 times higher levels of acetaldehyde in there breath or blood than that in nonalcoholics.
Inhaling Paint and Glue Fumes
Inhaling Lacquer Fumes
Swallowing Unleaded Gasoline
Bread Products of various types