Bryan College Station DWI

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Retrograde Extrapolation

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 [...]

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Intoxilyzer 5000 Machine Tolerance

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 [...]

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The Blood:Breath Partition Ratio

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 [...]

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Mouth Alcohol Interference

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 [...]

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Chemical Interference and the Intoxilyzer 5000

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 [...]

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Temperature and The Intoxilyzer 5000

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 [...]

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More On Henry’s Law

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 [...]

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The Intoxilyzer 5000

Driving While Intoxicated charges are some of the most difficult and technical cases to defend. Particularly, when a person provides a breath test sample to the police upon their arrest for DWI, a host of techincal issues arise that the qualified criminal defense lawyer must be familiar. This is the first of several posts to [...]

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Attacking the Horizontal Gaze Nystagmus (HGN) Test

The horizontal gaze nystagmus ("HGN") test is one used by police officers to establish probable cause to arrest a person for DWI. In theory, when used in combination with other field sobriety tests, HGN supposedly helps police officers correctly distinguish suspects who are under the influence of alcohol from those who are not. The test [...]

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College Station DWI Investigations Using Search Warrants For Blood

When a citizen is suspected of driving while intoxicated (DWI) they have the absolute right to refuse field sobriety testing, to refuse submitting to a breath or blood test, and to refuse to answer any questions that may incriminate themselves. However, the latest craze among Texas jurisdictions is for the police to obtain a search [...]

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