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All Georgia DUI blood tests are done using Gas Chromatography at the Georgia Bureau of Investigation crime lab.

What is Gas Chromatography?

Gas chromatography is a widely used scientific method of quantitatively analyzing the constituents of a mixture, see H.McNair & J. Miller, Basic Gas Chromatography (2d ed. 2009). Under standard blood testing protocol, the analyst extracts two blood samples and inserts them into vials containing an “internal standard”—a chemical additiveand places the vials into the gas chromatograph machine. Within a few hours, this device produces a printed graph—a chromatogram—along with calculations representing a software-generated interpretation of the data. 

Although the State argues obtaining an accurate BAC measurement merely entails “look[ing] at the [gas chromatograph] machine and record[ing] the results,” authoritative sources reveal that it is not that simple. “In order to perform quantitative analyses satisfactorily and . . . support the results under rigorous examination in court, the analyst must be aware of, and adhere to, good analytical practices and understand what is being done and why.” Stafford, Chromatography, in Principles of Forensic Toxicology 92, 114 (B. Levine 2d ed. 2006). See also McNair 137 (“Errors that occur in any step can invalidate the best chromatographic analysis, so attention must be paid to all steps.”); D. Bartell, M. McMurray, & A. ImObersteg, Attacking and Defending Drunk Driving Tests §16:80 (2d revision 2010) (stating that 93% of errors in laboratory tests for BAC levels are human errors that occur either before or after machines analyze samples). Even after the machine has produced its printed result, a review of the chromatogram may indicate that the test was not valid. See McNair 207–214. Nor is the risk of human error so remote as to be negligible. For example, in Colorado a single forensic laboratory produced at least 206 flawed blood-alcohol readings over a three-year span, prompting the dismissal of several criminal prosecutions, see Colorado Blood Testing Errors. An analyst used improper amounts of the internal standard, causing the chromatograph machine systematically to inflate BAC measurements. The analyst’s error, a supervisor said, was “fairly complex.” Ensslin, Final Tally on Flawed DUI: 206 Errors, 9 Tossed or Reduced, Colorado Springs Gazette, Apr. 19,2010, p. 1 (internal quotation marks omitted), Click to read.  

Why is Mass Spectrometry So Important?

Gas Chromatography/Mass Spectrometry has long been considered the “gold standard” for criminal toxicology laboratories. It is a strong analytical tool that uses the time it takes for the chemical to travel through the Gas Chromatograph’s column based on a substances known boiling point, the retention time (RT)the time it takes the substance to exit the loop or a tube as a gas after being subjected to heat, and temperature and pressure compared to known standards to identify the presence of alcohol. The amount of the alcohol is determined by using the area under the peak compared to a known amount of an internal standard, which is compared to a known amount of alcohol in a test run or calibration test.

How Gas Chromatograph/Mass Spectrometry  Works in Two Step Analysis:

1) The GC separates mixtures of chemicals into individual components.

2) The MS fragments the chemicals into unique patterns or spectra.

As the chemicals exit the GC column they enter the high vacuum chamber of the MS where the chemical is exposed to an ionization source that breaks apart the chemical into a number of ionized fragments, or an electron finger print. By controlling the ionization energy and “tuning” the MS, a reproducible fragmentation pattern or chemical (spectrum) or chemical finger print is created and compared to a reference database (library) of over 150,000 known chemical spectrum or finger prints. 

A good GC retention time combined with a solid MS spectral match makes this a truly definitive gold standard identification. With proper calibration and verification, the GC/MS can also determine the concentration of the chemicals detected. Without the Mass Spectrometry, there is no way to be sure that the chemicals leaving the loop or tube at a given retention time are alcohol. There are over 65 Million known substances in the universe any of which could have similar retention times at a given pressure and temperature. The Mass Spectrometry step eliminates this possibility.  

Chromatography Coelution and How Georgia Doesn't Use MS:

The Georgia Crime lab does not use Mass Spectrometry on alcohol tests. The Georgia Crime Lab uses an Agilent Gas Chromatograph model that does not have Mass Spectrometry capability. This leaves open the possibility of false positives or coelution. Coelution is basically a peak over lap on the chromagraph. Elution means the the substance exits the loop on the chrormatograph device. In other words, if two substances leave the loop at the same time they will be recorded as one peak. That is coelution. According to Agilent, "If any of the peaks overlap, accurate measurement of these peaks is not possible. If two peaks have the same retention time, accurate identification is not possible." What is Gas Chromatography? Agilent, Inc. A Mass Spectrometer can look at any point along a peak and give a probability percent of whether the substance was alcohol. Without mass spectrometry, you are simply hoping there is no coelution. 

What Are Those Unexplained Peaks at the Bottom of My Blood Test?

Many Georgia DUI blood test Chromatographs contain unexplained peaks. To see the Chromatograph, you have to get the "lab pack" from the Georgia Crime Lab. A Chromatograph is just a graphic representation of your blood sample and its contents. The internal standard will be marked on the Chromatograph which is usually rubbing alcohol. The Ethanol or alcohol from beer, wine and liquor will be marked on the Chromatograph. Unexplained peaks can mean fermentation, diabetes or other sources of extraneous alcohol or chemical interference. Unexplained peaks equals reasonable doubt.

Why All Georgia DUI Blood Tests are Subject to Reasonable Doubt:

With no verification by Mass Spectrometry, all Georgia DUI blood tests are subject to reasonable doubt. Don't be blinded by science. Hire a lawyer that knows how to fight and has beaten Georgia DUI blood tests at trial. Unfortunately, most of this type of information must be presented by expert testimony, and most prosecutors consider blood evidence the gospel truth. This means to fight a DUI blood test is expensive and almost always requires a jury trial, but it can be done because we've done it. 

If You refuse a Blood or Breath test, Police May Obtain a Warrant for Blood:

O.C.G.A. § 40-5-67.1 (d.1), provides, "Nothing in the Implied Consent Rights or Implied Consent law shall be deemed to preclude the acquisition or admission of evidence of a violation of the Georgia DUI laws if obtained by a search warrant as authorized by the Constitution or laws of this state or the United States."

This Amendment to O.C.G.A. 40-5-67.1 took affect on July 1st, 2006 and overruled State v. Collier, 279 Ga. 316, 317, 612 S.E.2d 281 (2005)(holding the plain language of OCGA § 40-5-67.1(d) restricts the ability of law enforcement to forcibly obtain that which has been refused).

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is a trial lawyer with 18 years of courtroom experience. He is one of only 6 Atlanta DUI lawyers with both an AV Preeminent rating from and a 10.0/10.0 Superb rating on He has over 100 "not guilty" verdicts under his belt and has forged indispensable relationships with police, judges and prosecutors all over the State of Georgia in order to benefit his clients' defense.
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No legal advice should be obtained from the web site alone. George C. Creal, Jr., P.C. is Georgia Professional Corporation authorized to practice law in the State of Georgia only and all information contained in this web site is intended for use for DUI arrests occurring in the State of Georgia. Individuals with DUI from outside the State of Georgia should contact a licensed attorney in the state of occurrence of their DUI. Copyright © 2014 George C. Creal, Jr. P.C.
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