The Real Truth About Alcohol Blood Tests

You want to know the truth?

Here it is, plain and simple: Blood alcohol tests are not always reliable.

That's good for a defense of your Wisconsin DUI charge.

But many people, and unfortunately many attorneys who should know better, believe that alcohol blood testing is a super-accurate, super-reliable piece of evidence in a drunk driving case. As this school of thought goes, a breath test may be challenged, but you cannot challenge a blood test.

This is nonsense. A blood test is only as reliable as the technician who did the test. There many sources of potential error in a blood test.

There are three main types of blood tests: enzymatic assays, headspace gas chromatography and direct injection gas chromatography. For a court case, blood tests are almost always either headspace or direct injection gas chromatography. Hospitals use enzymatic assays for medical purposes but these are not very good for legal purposes.

Here is a partial list of problems that can cause a false test result in gas chromatography (my top ten):

1. Out-of-date test tubes (very common);
2. Non-sterile or contaminated test tubes;
3. Delayed or faulty refrigeration of the blood (very common);
4. Bad preservative or anti-coagulant in the test tube;
5. Mixed up samples (the lab tech handles dozens of samples at one time);
6. Bad measurements during sample preparation;
7. Non-sterile equipment used during sample preparation;
8. Faulty calibration of the test equipment (this stuff is sensitive and must be constantly recalibrated);
9. Older, dirty or worn out components in the test equipment (also an ongoing problem, as the stuff gets dirty and clogged easily);
10. Failure to repeat the test process and double-check each step.

A competent drunk driving defense attorney will never settle for merely reading the blood test result. A competent defense attorney will review the lab records of all of the tests done by the technician in the same "run." He will review all of the maintenance and calibration records for all of the equipment used in the testing process and he will double-check the expiration dates on the seals and rubber tops to the blood vials.

If you are choosing an attorney, talk to him about these issues.
Remember: If you drink, do it responsibly.

If you'd like to speak to an attorney who knows about blood tests and other possible defenses to your Wisconsin DUI charge, then call me at 414-332-3499 or toll free at (877)DUI-DREW for a free, no obligation, initial consultation.

Return to Home