Collin County DWI Breath Testing: Why the Intoxilyzer 5000 doesn’t work by Plano DWI lawyer Troy Burleson
by Collin, Dallas and Denton County DWI Attorney Troy Burleson
One of the most argued points of law concerning the Intoxilyzer 5000 is the amount of assumptions that the machines internal “source code” makes when calculating a persons BAC (breath alcohol concentration). Until recently, the manufacture (CMI) has refused to turn over there source code to defense attorneys so that we can test the code for internal flaws. However, courts have begun to force CMI to turn over its source code and if CMI refused, courts have refused to allow the State to use the breath test result in trial.
On of the biggest assumption the Intoxilyzer 5000’s source code makes is that the machine is programmed to assume that the suspect has 2100 units of alcohol in his blood for every unit of alcohol in his breath. This is called the “partition ratio”. But this ratio is only an average: actual ratios vary from as low as 900:1 to as high as 3500:1
Why does this assumption matter to defense attorneys? It matters because if an individual partition ratio is different, the BAC result will be incorrect. If a person has a higher partition ratio (3500:1 for instance) than the assumed 2100:1, then the Intoxilyzer will give a result that is lower than the person’s actual BAC. If, on the other hand, the person’s has a lower partition ration (900:1 for example) than the assumed 2100:1, then the Intoxilyzer will give a result that is much higher than the person’s actual BAC.
For example: If a suspect has a true BAC of .06% (“not guilty”) and a partition ratio of 1300:1, for example, the machine will give a result of .10% (“guilty”) then the person will be convicted by a machine, not for being actually intoxicated, but for not being average in regard to his or her partition ratio.
