San Antonio DWI Blood Alcohol Concentration (BAC) Testing in Hospitals
I’m not talking about “privacy” here. I think we all know that if the government really wants to get into your business, it can and it will. This is just a fact of modern life. So, unless you live in a shack in the middle of northern Montana that is off grid and miles from the nearest roadway, someone in the government can contact you when they want.
No, I’m talking about the business of blood/alcohol testing and reporting. Hospital blood draws are not really (and scientifically they should not be) usable in a DWI trial to report an alcohol concentration. Yes, I know about the Texas Court of Criminal Appeal’s opinion in Somers v State , and its progeny. However, if one were to read the opinions and the details in them, the hospital “assays” (“tests”) were confirmed by another type of test to show that a drug or alcohol was detected , but the numerical results were not admitted. What is admissible from hospital blood draws in the DWI trial is the fact that ethanol was detected during photometric testing. Why?
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Hospitals Aren’t Forensically Certified Testing Laboratories
They are in the business of treating people medically – not the business of testing them for DWI trials. The purpose for testing blood in a hospital is to help guide the physician who is treating the patient, not the officer investigating a DWI. The results are not publicly reported, and the tubes of blood are destroyed after testing. Therefore, both cross-examination of a medical technician on her results and/or re-testing the blood are severely restricted. In fact, these rights are denied because the results are not intended to be used in a DWI trial. Also, doctors and nurses are very careful about patient privacy. They understand lawsuits: civil actions against them for violation of patient privacy. So, if hospital enzymatic tests were meant to be used by prosecutors, we would have no need for the Department of Public Safety (DPS) Forensic Testing Laboratory for blood/alcohol testing. Just take everyone to the hospital for testing, and we will have that blood/alcohol result in about ten minutes. No problem, right?
Wrong. Spectrophotometric testing (enzymatic assay) is not specific enough to produce an alcohol concentration. It is a screening test that must be confirmed under the Forensic Laboratory Guidelines that were adopted by the Society of Forensic Toxicologists and the American Academy of Forensic Science in 2006. The guidelines also specify that enzymatic assays must be confirmed by a secondary and more specific test. If you are in a hospital it’s probably because you were injured in an accident. That’s why you are being tested. The hospital staff does not get a warrant to seize your blood for testing. The only probable cause they need is the nature and extent of your injuries. By the way, their test does not test whole blood.
A whole blood alcohol concentration is what the prosecutor needs for a DWI conviction under Texas statutory law. The hospital blood tubes are either allowed to sit long enough for the red blood cells to fall to the bottom of the tube and clot or they are centrifuged down, crushing the red blood cells at the bottom. What is being tested is serum or plasma. After centrifuging your blood and before your serum is put in the machine for testing, an enzyme is added in order to allow the molecules to be detected by light at a specific wavelength, 340 nm to be specific. Only one small problem – the enzyme will react to alcohol and other substances in addition to alcohol in order to produce the measurement.
Okay, you were injured, right? You were bruised. You dislocated something, and it is swollen. You might even have broken a bone or two. That’s why you are in a hospital and not in a jail! Well, your body does some things in and around those injured places. It produces lactate and lactate dehydrogenase that get into your blood stream. I’m not here to tell you why. Go look it up on Google. The fact is that these chemical compounds are also detected by light at a specific wavelength, 340 nm to be specific. Therefore, the enzymatic measurement for alcohol concentration is wrong – really wrong! Don’t take my word for it. See, Serum-ethanol determination: comparison of lactate and lactate dehydrogenase interference in three enzymatic assays , Nine JS, et al. J. Anal Toxicol. 1995 May-June. The measurement may add to ethanol, it can spike at a particular time or it can produce a false positive for alcohol.
By the way, law enforcement didn’t like this study, and they had other researchers try to rebut it. Problem was, the other studies (like Somers v State ) used other chemical tests to confirm the amounts in serum or they actually tested for lactate and lactate dehydrogenase during their analysis in order to subtract it from the overall measurement. Again, there was no whole blood analysis. The problem is that hospitals usually don’t test the average patient in the ER for lactate while treating her for accidental injury from a car crash. Also, they don’t care about whole blood analysis for alcohol concentration. AND they don’t care about this whole debate. They want the courts and the lawyers to leave them alone!
But, every now and then, in a small town, or in a case where some officer feels that he was denied the right to fully investigate, or some prosecutor just insists on getting that number because without it he has NO DWI CASE, the enzymatic assay suddenly becomes: **scientifically reliable!** He figures out that he can convert the hospital serum analysis results to a whole blood number. It’s simple! You just use the well-known “serum to whole blood alcohol ratio” while (ahem!) ignoring the inconvenient fact that other substances are measured in that serum at 340 nm. (Let’s see… ? x .20 = ? – uh, never mind…)
Contrary to the State’s assertion, the serum/whole blood alcohol ratio is concentration-dependent, with average values ranging from around 1.12 to as high as around 1.18, depending on serum alcohol concentration. There is no generally applicable serum to whole blood conversion factor. Again, don’t take my word for it. J Anal Toxicol. 2007 Jan-Feb;31(1):23-30 Comparison of hospital laboratory serum alcohol levels obtained by an enzymatic method with whole blood levels forensically determined by gas chromatography. So, the formula for hospital serum to whole blood conversion is actually: ? x ? = ?. Quod erat demonstrandum !
Law, science, common practice, and common sense demonstrate that chromatographic forensic testing is the standard for courtroom BAC evidence. If Texas courts have ruled that enzymatic assays were the forensic standard for BAC evidence, we would not need the DPS Forensic Toxicology Laboratory for BAC testing. I don’t think they are going to do that. Otherwise, who else would we have to harass in the courtroom?
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