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Blood Test Issues

Blood Test Issues

The following information is adapted from a discussion of issues in a Blood Case was delivered by Attorney Ed Loss to Judges and Members of the Defense Bar at an Arizona DUI Symposium in February of 2000.

1. The Blood Draw

The person who actually draws the blood from an individual accused of DUI must be TRAINED to do venipuncture / blood withdrawal.

How did the person performing venipuncture CLEAN THE SKIN before the needle was inserted? Hospitals often use isopropyl alcohol to clean the site. This which can CONTAMINATE the blood sample. Also, if "NIK kit" used, ask in discovery for content of forensic swab. If betadyne, Alcohol is an "inert" ingredient.

2. What was tested? Whole blood or plasma?

Whole blood is composed of cellular material, plasma and fibrinogen (clotting agent). Hospitals test serum or plasma (whole blood is FILTERED to remove the cellular material and fibrinogen).

MEDICAL blood draws are primarily concerned as to whether alcohol is on board (like a "yes or no" answer). FORENSIC blood draw, on the other hand, is concerned with precise concentration.

Testing plasma or serum is less messy than testing whole blood, but there are PROBLEMS WHEN TESTING PLASMA (e.g. when you centrifuge the blood sample, you take the solid, cellular material out, but you leave the same amount of alcohol in a smaller volume of liquid). This process artificially RAISES the concentration of alcohol in the liquid-which can lead to a skewed test result if blood is being drawn as EVIDENCE IN A DUI CASE. Hospitals test serum or plasma but report it as "blood alcohol." The test of serum or plasma IS NOT GOOD ENOUGH to use for DUI evidence!

Serum is plasma with the fibrinogen (clotting material) removed. Serum is collected when the blood sample is allowed to actually clot. When the blood clots, a clear liquid (serum) forms over the blood. Serum and plasma alcohol concentrations are not much different. HOWEVER, both of these tests are VERY different than analysis of WHOLE BLOOD.

If whole blood is NOT analyzed, blood alcohol content will appear to be HIGHER (on average, serum or plasma BAC measurements average about 16% higher than whole blood).

Bottom line is this: You must ask the lab tech: "Did you centrifuge the blood?" "Did you test serum / plasma or whole blood?"

3. Hematocrit

Hematocrit is the PERCENTAGE of your whole blood that is made up of cellular material. If someone has a Hematocrit of 47, we are saying that 47% of their blood is made up of cellular material, and the remaining 53% is plasma (mostly water). The normal range for a male is 47%-- slightly lower for a female.

What happens if someone had a Hematocrit of 60; i.e., he had a higher percentage of cellular material, and they tested plasma? ANSWER: You're going to get a higher BAC because you have a lesser volume of liquid. Alcohol will always gravitate toward the liquid. So--you have a higher BAC result with higher Hematocrit. The higher alcohol concentration results from the alcohol being contained in a lower volume of liquid (the plasma). Note also that trauma can result in a lower Hematocrit. Hospital records will usually show Hematocrit.

4. IV fluids given before blood draw

Wouldn't more liquid tend to dilute the Alcohol and give someone a lower BAC reading because the total volume of liquid INCREASES because of the IV No! Alcohol tends to follow water in the blood. When you consume alcohol, you don't just have alcohol in your blood stream. You have alcohol in your body tissues as well. If you increase the liquid (as a result of IV fluids), that liquid tends to pull more alcohol out of the tissue and artificially increases the individual's BAC.

5. Blood Test Kits

  • Expiration Date. Blood test kits (formerly Becton-Dickinson) now manufactured by NIK Public Safety Inc. THESE KITS HAVE EXPIRATION DATES. After the expiration date, the vacuum in the VACUTAINER TUBE is NO LONGER WARRANTED.

Each vacutainer tube contains a preservative and an anticoagulant. A precise vacuum in the tube exists to insure that a precise amount of blood will be drawn and mixed with these chemicals in a specific ration. If there is too much chemical and not enough blood, this can AFFECT YOUR TEST RESULT because the preservative and anticoagulant are "salting out agents."

  • Salting out chemical. In addition to the N-Propel alcohol, the lab adds a chemical to the mixture to help the alcohol get out of the liquid and into the vapor. The higher the concentration of salting out agent, the more alcohol in the vapor. Too much salting out agent will erroneously put too much alcohol in the vapor than should be in relation to the alcohol in the liquid. This brings us back to our chemicals in the vacutainer tubes. Sodium fluoride and potassium oxalate are salting out agents.

If a vacutainer leaks, microorganisms from room air can enter the blood sample. FERMENTATION results when the blood sample is combined with microorganisms. ALCOHOL is a byproduct of fermentation. There is NO WAY to distinguish between alcohol consumed by a subject and alcohol CREATED BY FERMENTATION.

Another question to consider: "Did the lab test the blood for bacteriological contamination?"

  • Chemicals in vacutainer tube. Each vacutainer kit is intended to take 10 ml of blood. Each kit contains two chemicals: 100 mg of sodium fluoride (a preservative to prevent fermentation and neo-production of Alcohol) and 20 mg of potassium oxalate (an anticoagulant designed to prevent clotting of the blood).

The first question you must ask is, "Were these chemicals in the vacutainer tubes?" These chemicals are critical to an accurate test result. Did the person drawing your blood check the vacutainer tubes to confirm that powder was in the tubes?

Where was the blood kit kept prior to the blood draw? In the trunkof the police car? For how long and under what conditions?

  • Instructions in blood kit. NIK kits have two sets of instructions. One for the person drawing the blood and one for the cop. One of the instructions pertains to MIXING of the blood immediately after the blood draw. After the blood is in the vacutainer, the person drawing the blood is to invert the tube 5 times. Then, the cop is to invert each tube 20 times. Tubes must not be shaken. Purpose of inversion ritual is to assure proper mixing of blood and chemicals in tubes.

6. Chain of Custody

Is there a "secure refrigerator" with a log book? A "break" in the chain of custody typically does not prevent evidence of your blood test from being admitted at trial, but it CAN go to "weight of the evidence" (i.e. with poor chain of custody, the evidence is not going to be taken very seriously).

7. Gas Chromatography

Gas Chromatography (G/C) is a method of (a) identifying a substance and (b) determining the concentration of that substance. Several avenues of attacking the gas chromatograph exist including: 1) presence of too much of the "salting out chemical" in the original blood sample-which can ARTIFICIALLY RAISE THE ALCOHOL LEVEL MEASURED, 2) core body temperature variations can CHANGE the expired breath variation and can ARTIFICIALLY INFLATE A BREATH TEST READING in a particular type of GC called "head space gas chromatography.


They didn't check to confirm the chemicals were there."

"They didn't do the things necessary to assure a proper mix between the blood and the chemicals in the vacutainer tubes."

Were the chemicals in tubes in the proper concentration?

"They didn't look." "They didn't know." "They didn't care."

Potassium oxalate - The anticoagulant. 20 mg of potassium oxalate is used to prevent blood from clotting. Remember, if blood clots, the alcohol goes to the liquid and increases BAC reading. Potassium oxalate combines with calcium ions in the blood to prevent formation of flambin. Flambin is a clotting element. If blood clots, we are going to get a higher Alcohol concentration in the liquid above the clot. Any clotting is going to raise the BAC. After the blood draw, but prior to analysis, you can do a test to determine if the anticoagulant is present. That test is call "Ion Chromatography."

ASK THE LAB TECH: "Can you do it?" "Did you do it?"

We are establishing a theory that the lab just didn't care to perform the tests necessary to assure a higher than accurate test result. What if the lab guy says, "Well, if the blood clotted, I would have seen it upon visual inspection." WRONG! Blood can form micro clots that can't be seen upon visual inspection.

Sodium Fluoride - The Preservative. The 100 mg of sodium fluoride is a preservative to prevent formation of Alcohol by fermentation of the blood. Fermentation of blood can have a dramatic impact upon Alcohol concentration. A blood sample with no alcohol can generate .25% BAC or higher as it decays. This "neo-genesis" type of alcohol cannot be distinguished from the alcohol they are testing for. Refrigeration will slow down the fermentation process, but not prevent, fermentation and the production of alcohol.

Where do preservative and anticoagulant come from? NIK purchases the chemicals commercially, in bulk. Then, NIK mixes them in bulk. A measured amount of each chemical is dropped into the vacutainer tube as it goes down the assembly line. NIK does not sample the vacutainer tubes once the chemical is in it. The presence, and amount, of chemical is critical. If the tubes aren't tested, how do you know them chemicals are there and there in the proper concentration?

Questions for lab technician. "You've never tested a vacutainer tube to determine if the proper concentration of chemicals were present"? "You couldn't be bothered to confirm that just one of the tubes had the proper amount of chemicals in it"?

A.W. Jones is on record that, in order to prevent fermentation, you need 100 mg of sodium fluoride in the tube.

Interesting Demonstrative: Compare state's dark, gunky blood with bright red blood from a fresh blood draw. (Perhaps client will volunteer for a de novo blood draw)

Machine error. Like the IR 5000, the G/C has a 10% margin of error under our administrative regs. A 20% margin of error is not uncommon. The process is not that precise.

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