Blood drawn for a forensic blood test will in almost all cases be taken from the suspect via a vacutainer, which should contain two substances -sodium flouride, a preservative, and potassium oxalate, an anticoagulent. Further, they are vacuum sealed, which explains why they are called vacutainers .
Most vacutainers in use are made by Becton Dickinson. They also have an expiration date, after which the vacuum seal is no longer warrantied. BUT, very few phlebotomists, police officers, or state crime lab personnel pay any attention to the expiration date. Simply stated, nobody checks.
Becton Dickinson only checks one out of every four thousand vials for quality control. There are at least three possible defects in the state’s blood test:
1. A bad seal on the vacutainer, which is impossible to detect after the test, because it has been opened.
2. Improper amount of sodium flouride in the vial. Since vials are routinely nor refrigerated prior to their delivery to the crime lab, the proper amount of sodium flouride is critical. Either too much or too little can lead to a false high test result and
3. Improper amount of potassium oxalate. In the case of a bad seal organisms from the environment, such as candida albicans, can get in. Unless there is enough sodium flouride in the vial, the organisms that may be in your client’s blood will grow. One such organism is the ubiquitous candida albicans, which is is a yeastlike organism that is resistant to sodium floride. In the presence of glucose and warmth, it will excrete ethanol via fermentation.
Too much sodium flouride may cause “salting out”, which will also lead to a false high test result with headspace gas chromatography. This can occur even if there is no problem with the vacutainer, but the phlebotomist draws too little blood.
If there is not enough potassium oxalate, the blood can coagulate or “micro-coagulate” which is almost completly undectable. Because this changes the ratio of liquid to solid in the substance that is tested, and ethanol is water soluble, it can lead to a false high test result.
It can be virtually guaranteed that in any case involving a blood test the lab did not test for the presence of Candida Albicans, the lab did not check the vial seal, and the lab did not check the amount of sodium flouride or potassium oxalate in the tube.
If any of these occurred, you will in all likelihood have a false high blood alcohol concentration reported by the lab.