Bryan-College Station DWI

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“Using SFST Validation Studies in Your Next DWI Trial”

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 [...]

By | August 12th, 2015|"Off The Back", Bryan College Station DWI|1 Comment

“Quick-and-Dirty Phlebotomy Basics”

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. [...]

By | December 5th, 2014|"Off The Back", Bryan College Station DWI, Courtroom Trial Practice|Comments Off on “Quick-and-Dirty Phlebotomy Basics”

Should You Blow During Your Next DWI Stop?

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 [...]

By | January 4th, 2013|Bryan College Station DWI|Comments Off on Should You Blow During Your Next DWI Stop?

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 [...]

By | January 4th, 2013|Bryan College Station DWI|Comments Off on Retrograde Extrapolation

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 [...]

By | January 4th, 2013|Bryan College Station DWI|Comments Off on Intoxilyzer 5000 Machine Tolerance

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 [...]

By | January 4th, 2013|Bryan College Station DWI|Comments Off on The Blood:Breath Partition Ratio

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 [...]

By | January 4th, 2013|Bryan College Station DWI|Comments Off on Mouth Alcohol Interference

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 [...]

By | January 4th, 2013|Bryan College Station DWI|Comments Off on Chemical Interference and the Intoxilyzer 5000

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 [...]

By | January 4th, 2013|Bryan College Station DWI|Comments Off on Temperature and The Intoxilyzer 5000

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 [...]

By | January 4th, 2013|Bryan College Station DWI|Comments Off on More On Henry’s Law