Blood Alcohol Tests: Not as Reliable as You Think

Posted on May 8, 2014

Car Keys and Drink

Blood analysis for alcohol content is a process that many jurors in DUI trials do not understand. If your DUI trial involves such evidence, your Redwood City DUI law office may want to inform the jurors of the pitfalls associated with blood analysis. Jurors often believe that scientific evidence is infallible and that a technician or scientist somewhere gave the evidence personal attention in order to analyze it. This is rarely the case; in fact, the technician is often not even in the same room as the blood sample when running the entirely automated analysis. If the blood analyst is called by the prosecution to testify about the evidence, your attorney can try bringing that out on cross-examination.

Attorney: Did you perform the analysis on the defendant’s blood?
Analyst: Yes, I performed it myself.
Attorney: When you say you performed the analysis, does that mean you operated the machine that did the analysis?
Analyst: Yes. It was a gas chromatograph.
Attorney: When you performed this analysis, were you only analyzing my client’s blood or did you analyze other samples in a batch?
Analyst: There may have been a few others.

Your Redwood City DUI lawyer will understand that the witness is trying to shade the truth by hiding how large the batch of samples was. Often, forensic experts who are called to testify in DUI cases do not expect a line of questioning this specific. They do not expect defense attorneys to know that much about how forensic evidence collection works.

Attorney: How many others? 40?
Analyst: Yes, about that many.
Attorney: How long did this all take?
Analyst: About a couple of hours.
Attorney: So, were you in the room during all of those hours while the samples were being analyzed?
Analyst: Well, not all the time because the test is automated.
Attorney: So, it fair to say that you may not have even been in the room while the analysis of the defendant’s sample was being performed?
Analyst: I suppose that’s possible, yes.

It is important that you understand the merits and the weaknesses of scientific evidence in your DUI case. For more information, call a Redwood City DUI law office Silveira Law. Call (415) 795-3890.