DUI Blood Testing in Georgia

Many prosecutors, police, and uneducated DUI defense attorneys think that blood tests are the gold standard when it comes to determining a DUI suspect’s BAC.  Often defense counsel will roll over when faced with a blood test that is above the legal limit because they don’t know how to attack the results.  Blood tests performed by the State of Georgia are not reliable when it comes to determining a person’s BAC.  The reasons for this are numerous, and it would take pages to explain them all, so I will mention the most interesting one’s here.


When you or I go to the doctor for a blood test the medical lab performs tests on our actual blood (either whole blood or serum).  Most people think the same is true when the State of Georgia performs its BAC tests on a blood sample, but this is not true.  The Georgia Bureau of Investigation (GBI) who performs the test uses the same principle for testing blood that the Intoxilyzer 5000 breath machines use.

The breath machine operates of Henry’s Law.  Whenever I hear something scientific I tune out so I will make this very simple.  Henry’s Law states that in a closed environment any gas above a liquid will contain an equal ratio of any substance contained in the liquid.  So, the closed system is your lungs, the liquid is your blood (containing alcohol), and the gas above the liquid is your breath.  The alcohol diffuses from your blood into your breath, and then the machine uses as 2100:1 ratio to “estimate” your BAC.

The 2100:1 ratio is important because if you burp, vomit, or have alcohol in your mouth it will not have gone through your body and been broken down so the machine may apply the 2100:1 formula to it.  The pure alcohol will go straight into the machine thus causing a high false positive.  Remember this fact for later.

This same science is applied to Georgia DUI blood testing so your actual blood is never tested.  The closed system is the test tube, the liquid is still your blood (containing alcohol), and the gas is the air above your blood in the test tube.  So, the blood measuring machine at the GBI puts a needle into the air above the sample, takes a sample, and applies the same faulty science as the breath machine.  Therefore, on a Georgia DUI blood test, your actual blood is never analyzed.  Only the air above it in the test tube is analyzed.


As if the above-mentioned problem isn’t worse enough your test tube of blood, and the air it contains, is not the only one being sampled by that needle. The Georgia DUI blood testing machine at the GBI Division of Forensic Sciences tests 33 test tubes in a row using the same needle to test each sample. Remember, the machine is testing the air above the blood.  The machine is not testing the actual blood itself.

Your test tube of blood does not get its own clean, independent needle for testing.  Does that sound scientific to you?  Also, there are no controls while the 33 samples are being measured. There are 3 controls at the beginning of the 33 test tube sequence, and 3 controls at the end.  If the machine does not detect any errors while testing the 3 controls at the beginning of the sample, and it doesn’t detect any errors when it tests the 3 controls at the end of the 33 tube sequence the machine assumes it did not malfunction or commit any errors while testing the 33 tubes.

Therefore, if the machine did malfunction during the 33 test tube sequence no one would ever know.  If the machine “fixes” itself before it hits the 3 controls at the end of the 33 tube sequence the machine will assume it was functioning properly.  In short, there is no independent control for each individual test tube.

Further, the machine tests each sequence of 33 tubes 2 times. However, between the first and second test, the tubes are moved from one machine to another.  A person, not a machine, must move these tubes and re-label them.

Human error is a big problem here.  Imagine if you had to move tubes all day, and re-label them in perfect order.  Do you think you’d never screw up and mismatch one?

For instance, if your test tube is number 18, and it read .04 (way below the legal limit) on the first test, and the technician mismatched your vial on the transfer to the second test with number 19 which contains .20 (2 and a half times the legal limit) there is going to be a huge problem with the final analysis of your blood.

Of course, the machine won’t catch this because it only checks itself against the 3 controls at the beginning of the test, and the 3 controls at the end of the test.  There is nothing to tell the machine that something happened, and the vials were accidentally switched.


For a Georgia DUI blood test, the technician who draws your blood must be qualified to do so.  Additionally, the procedures they follow or fail to follow, can have a profound effect on the results of your blood test.  Even though Georgia law requires there be certain procedures for all state-administered chemical tests there are no written regulations or procedures for Georgia DUI blood testing.  However, there are some universal procedures that should be followed.

What is one of the first things a technician does before inserting the needle into your arm, or another area? They disinfect the area.  The technician is supposed to use a disinfectant other than alcohol, but this is not always the case.  While it doesn’t seem possible that a needle passing through alcohol-soaked skin will pick up enough alcohol to affect the test results nothing could be farther from the truth.

Remember the 1200:1 ratio discussed earlier, and how if you belch, vomit, or have to mouth alcohol it can affect your BAC reading because pure alcohol will cause a high false positive?  The same thing happens here.  Since the blood test is performed using the 1200:1 ratio any alcohol that goes directly into the sample is going to greatly increase your blood alcohol content reading.  It is very important that the technician not use alcohol swabs to disinfect your arm before drawing blood.

An interesting fact about test tubes is the stopper on top of each tube.  The color of the stopper indicates what is contained inside the test tube.

The 2 most common colored stoppers for Georgia DUI blood testing are grey stoppers and red stoppers.  The grey stopper indicates that the tube contains a preservative (usually sodium fluoride), and that the same should be saved after testing just in case-independent testing is requested.  The red stopper indicates that there is no preservative in the tube, and the blood sample should be discarded after analyzing it for alcohol.

In test tubes that contain preservatives, it is EXTREMELY important that the technician invert the test tube 14 times after the blood is in the vial. This is to ensure that the preservative agent gets mixed into the blood. Often times the test tube is not inverted the proper number of times, and the preservative does not mix into the blood samples.

I often equate this to mixing a protein shake, smoothie, etc. Do you know when you blend, or stir, the powder and then pour your drink into the glass there is always that glob on the bottom of the blender where the powder wasn’t mixed into the drink? The same thing happens here.  What happens if the preservative is not in the blood sample, and the sample begins to deteriorate?  A by-product of blood decomposition is alcohol.

Additionally, blood samples must be refrigerated after they have been collected.  Again, this is a step that is often neglected by the lab or the GBI once the samples arrive at their laboratory.  It is not uncommon for the specimens to sit at the GBI, at room temperature for days waiting to be tested.

Further, preservatives added to the blood and refrigeration will not stop blood decomposition, but merely slow it down.


Since the GBI keeps some samples at room temperature waiting to be tested, and because some police units mail the specimens, unrefrigerated, to the GBI the blood begins to decompose.  Since blood is an organic material it will decompose as a reaction of enzymes to heat and as a result of bacterial action.

This is known as endogenous blood alcohol production or microbial fermentation. Blood without a preservative, at room temperature, is reliable for about 2 days. Without sodium fluoride or other preservatives, the BAC will rise to a maximum in about 15 days. In a blood sample containing no alcohol, decomposition can cause a BAC reading of 0.25 (more than 3 times the legal limit) or higher depending on the stage of decay.

Remember, these in vitro blood changes are brought on by the drawing and improper storing of the blood sample.


Most blood tests are conducted on blood plasma because it is easier for the laboratories to perform their tests on blood plasma.  However, testing whole blood is more accurate.  It is not uncommon to see variations in the results of the same blood sample when the sample’s blood plasma is first analyzed, and then the sample’s whole blood is analyzed.  False high readings will result when blood plasma is tested instead of whole blood.

Additionally, there is strong evidence that blood serum samples due to their lack of accuracy show a lack of trustworthiness as evidence of a person’s actual BAC.  Every individual has a different serum/whole blood ratio that differs from 1.09 to 1.35.  The machine testing the blood sample uses an arbitrary, average, or “one size fits all” conversion ratio when it is computing a blood sample’s alcohol content.  This average conversion rate does not give accurate results for each individual since it does not take into account that person’s actual serum/whole blood ratio.