Mimi Coffey in a Gas Chromatography Lab 2023 Everyone knows you can’t compare apples to oranges yet this is what many Texas forensic laboratories are doing. ANSI/ANAB standards (who accredit Texas crime labs) are very specific on both quality control and method validation requiring some whole blood samples to be tested to adjust for the matrix effects that blood samples introduce in gas chromatography testing. Yet, most north Texas labs still ignore these “shall” (not optional) mandates opting to use aqueous samples (water based). Blood has compounds that interfere in analytical readings that water based calibrators and controls go not have. Does this affect the result? 100%. Absolutely. One study in Austin estimated an increase in alcohol (ethanol) by 20%. This is just one Texas government lab’s findings. Bottom line- don’t trust the blood result. The State must do better.
People think DWI blood tests are 100% accurate. Yet this is not true. People assume that a blood score is like DNA evidence- irrefutable. Once again, this is not true. People give up hope and resolve to plead guilty or no contest to their DWI thinking it is impossible to win. This is sadly not true. I was abhorred when a Houston blood expert (Ph.D in chemistry and former state lab forensic scientist) explained to me that if the lab tech accidentally pipettes one quarter of an extra drop into the test tube the score can be .07 too high! I was equally mortified when I learned that many results come from labs that do not properly validate their machines. A result is only as good as its measurements. These measurements must be properly tested (lower limit of detection, etc.) before one can rely on them. In June of 2023 I will be spending a week in a university gas chromatography lab teaching other lawyers about the issues with testing. This will be my second time in this particular lab la