Quite often I am confronted with a dilemma in my DWI cases, the question of how do I properly explain the breath test to a jury. Afterall, many people believe that this machine is accurate, is reliable, is accepted, and is the determiner of guilt or innocence in a DWI case. I have spent countless hours studying, analyzing, and dissecting this police tool of expedient-fast-cheap analysis of a person's breath.
The box spits out a number, a result, a reading and nothing more. I believe juries must look at all the evidence before they just buy the reading as a Truthful, Accurate, and Reliable number.
1. This machine does not check blood. It measures breath alcohol. It is a better screener (qualifier) than assessor (quantifier). It indirectly takes a breath measurement, and then gives a blood alcohol number.
2. This machine operates at 34 celcius. People do not all possess a breath temperature of 93.2 F (34 celcius) because not everyone is 98.6 F (body temperature).
3. This machine only requires (by current state law and case law) yearly calibration.
4. The machine only takes ONE breath sample, ONE time. There is NO confirmation of testing. This is another expedient NYS standard. Scientific-forensic standards be damned. We would never accept (one test-one result) this from a blood test, an MRI, or an X-ray but in the world of NYS DWI ths is the standard.
5. This machine is allowed a 20% range of error by law. The simulator solution (standard of known alcohol measure) can be .01 BAC up or down (higher or lower).
6. Contamination is not only possible it is probable. The inside of the machine is never cleaned unless there is a break down. This machine has lenses, mirrors, and filters. Hundreds of people breath into this machine. How common is dust, dirt, mouth chew, smoke, and an assortment of other expectorated particles? How clean is your average police station? This is certainly not a lab environment with standards of hygiene. Forensically this is a nightmare. Consider that the machine works (operates) by passing light through a tube filled with breath. Whatever light is absorbed by alcohol in the breath determines the breath alcohol number. If other substances (crap in the tube) absorb the light you got a bigger BAC.
7. They "clean" the tube with an air blank before and/or after your test. Can you really clean a tube with an air blank?
8. The machine self checks. It basically checks itself. Can we really trust and place our faith in a computer that has no outside checks?
9. The machine allows errors, and still gives a reading. If insufficient sample comes up on the machine display the reading is still used. What insufficient sample really means is that the machine needs (requires) 1.1 liters of breath to give a read BUT will often read without that amount. Smaller sample means more concentrated alcohol. Think of it this way, two glasses of milk, one bigger, one smaller, same amount of chocolate, the one with less milk is darker chocolate milk, one with more milk is lighter chocolate milk.
Lower BAC with greater air volume, and higher BAC with lower air volume.
The problem with machine defense is this, global atacks on breath testing are not usually successful. Breath testing is here, it is accepted, and it is used nationally. In each and every DWI defense breath testing can be successfully contested (challenged) if that particular breath test, on that particular day, and with that particular individual has an issue (s). Breath testing may be cheap, inexpensive, and easy but it is my mind far from reliable in the majority of cases.