At this point we all know that the breath machine, in Maryland it’s the EC/IR, in DUI/DWI cases is a vital part of the DUI conviction process; that’s why the legislature has its very own law for blowing a number of .08 or greater into the contraption. The law is known as Maryland Transportation Article 21-902(a)2 or the per se law. This law says that if you blow a .08 or higher, your are in violation of this statute and therefore you are GUILTY of this crime, irrespective of any other details regarding your case. Pretty stringent huh? Particularly if you consider that these machines are not particularly accurate in determining a person’s BAC (blood alcohol content).
How can I say these machines are not particularly accurate? Well, don’t take my word for it, I’m just a lawyer. However we should take the word of very learned and highly regarded experts in the field who have written numerous articles on these machines. In a nutshell, the machine utilizes a partition ratio (a formula) to calculate the ethanol that it senses on ones breath and to extrapolate out what it believes a person’s blood alcohol content should be. The machine then spits out that number on a cash register sized piece of paper and you then have to fight the machine or be convicted of DUI.
The problem is that the machine utilizes a constant partition ration number of 2100:1 for all people. So the machine multiplies the parts of alcohol that it senses in the breath, it calculates that number by 2100 and it says the result is your BAC or blood alcohol content. Big, small, tall, short, male, female, black, white, Asian makes no difference the machine calculates 2100:1 partition ratio. Are all people made alike? Does the 6’8″ NFL player have the same body makeup as the 5’2″ soccer mom? I don’t think so and either do the experts in the field.
The reality is that we all have different partition ratios that can range from as low as 1500:1 to as high as 2500:1 or higher. The machines however are programmed to take an average number of the average person. The problem is that we are all not average people, if we were we would all be 5’9″ and 170lbs. So when the machine uses the wrong number, which does not match the partition ratio of the person tested there is a substantial chance that the number the machine yields will be erroneous; it could be erroneous by as much as 10-20% or more.
In addition to the foregoing, the method of the blow, or how you blow into the machine also has an impact on your number. There is a saying among those that work in field “the harder you blow, the higher you go” so when the breath test technician tells you to hold your breath and blow in the machine as hard as you can he is really saying “lets artificially maximise the number that you blow so that I can get an easier conviction in court.”
The machine requires a steady exhalation from the defendant which should last roughly 5 seconds in duration, the machine then measures the volume of ethanol in the trailing exhalation right before the volume of breath dissipates. If you hold your breath and blow as hard as you can, you are artificially maximizing the volume of ethanol exhaled into the machine from the deep lung which is then calculated at the partition ration as described above.