The National Highway Traffic Safety Administration (NHTSA) spent many thousands of dollars on studies to develop a battery of DWI investigation tools called field sobriety tests. The studies were funded by NHTSA to validate and standardize the Horizontal Gaze Nystagmus (HGN), the Walk-and-Turn, and the One-Leg-Stand tests. Standardization meant developing a method of administering and interpreting [...]
The DWI blood test case is becoming the stock-in-trade of many law enforcement agencies across the state. Whether it's a sample provided voluntarily after arrest, or obtained via search warrant following a refusal, defending blood tests are now commonplace for the DWI defense attorney. Making preparation more demanding is the technical nature of these cases. [...]
Should you submit to a breathalyzer the next time you're the focus of a Bryan-College Station DWI investigation? For years the standard operating procedure (SOP) for DWI suspects was "DON'T BLOW." That is, once you were arrested for DWI/DUI in Brazos County the best defense was a good offense. Citizens accused were encouraged by DWI [...]
The present installment in this series on the Intoxilyzer 5000 involves the concept of retrograde extrapolation. Retrograde extrapolation is the process of calculating the alcohol concentration of a person at a time earlier (the time of driving) than the time of a breath test. Retrograde extrapolation is not technically a defense against the science or [...]
Every machine created by man has tolerance for error including the Intoxilyzer 5000. For the Intoxilyzer this error tolerance is reported in grams of alcohol/210 liters of breath. It's just another source of erroneous breath test results for persons accused of DWI. During a subject test the Intoxilyzer will first analyze the vapor from [...]
In our previous study of Henry's Law we learned when a volatile chemical (ethanol, for instance) is dissolved in a liquid (blood) and brought into contact with a closed air space (the lungs), an equilibrium is formed and there exists a fixed ratio between the concentration of ethanol in the air space and the concentration [...]
Mouth alcohol is another potential source of error with the Intoxilyzer 5000. If alcohol is regurgitated into the mouth (by burping or belching) and absorbed into the mouth tissues, it will effect the breath test result by overestimating the amount of alcohol attributed to the breath sample. Even the act of forced exhalation required to [...]
Today we'll look at another potential source of error with the Intoxilyzer - volatile chemical interference. The Intoxilyzer 5000 uses a method of quantitative analysis called infrared spectroscopy to determine how much ethanol is present in the breath sample of a DWI suspect. Simply put . . . different molecules absorb infrared light at [...]
One of the most neglected areas of attack upon the Intoxilyzer 5000 by Texas criminal defense lawyers defending DWIs is the assumption the temperature of a DWI suspect's breath is 34 degrees Centigrade (or 93.2 degrees Fahrenheit). Heat is the driving force behind Henry's Law and the inner workings of the Intoxilyzer 5000. Heat [...]
Earlier we examined the problems with the Intoxilyzer 5000. This machine is used nationwide by law enforcement to obtain breath samples from DWI suspects and to analyze the sample for ethanol concentration. More on Henry's Law. The reference sample device on the Intoxilyzer is designed to deliver a sample of vapor containing a known or [...]