Blood Tests


Laboratory analysis of DUI blood samples – blood tests.

How a crime lab analyzes DUI blood samples is a major issue. From the accreditation of the lab, to the preparation of the samples, to the instruments used in testing, there are numerous potential pitfalls.

The most common form of blood laboratory analysis is called Gas Chromatography, a process in which a sample of blood is analyzed using a Gas Chromatograph instrument. Gas Chromatography is currently the most popular method for analyzing B.A.C. levels in a blood sample of a DUI suspect. There are two methods of Gas Chromatography analysis, headspace gas chromatography and direct injection chromatography. In addition to Gas Chromatography, another less commonly used method is called the Enzymatic Method.

Chain of Custody For Blood Samples In DWI Cases

In order for a DUI blood test result to have any evidentiary value in court, a proper chain of custody must be kept. The prosecution must lay a proper foundation in order to admit blood test results in court. For a sample to be admissible, the prosecution bears the burden of establishing:

-The person who drew the blood;
-That the person who drew the blood was qualified to do so;
-The time and location the sample was taken;
-The circumstances under which the sample was obtained;
-The labratory technician who analyzed the sample;
-The qualifications of the lab technician;
-That the sample was accounted for the entire duration of testing
-That the testing instrument the sample was analyzed on was properly calibrated and maintained;
-That the method of testing was an established method commonly accepted in the field;
-That the sample was properly preserved and stored prior to testing and during transport.

Any time the blood sample changes hands, a document must be signed and dated, with the time of receipt acknowledged. This is to ensure that someone is responsible for the sample at all times, to prevent any chances of tampering with the evidence. Rules specify where the blood sample is to be kept and stored during transport, as well as the timing requirements. If a sample does not comply with certain procedures, the judge may determine the BAC results to be inadmissible. Additionally, the prosecutor may even decide to dismiss the case.

If you have been arrested for DUI and were subjected to a blood draw, contact an experienced DUI defense attorney in your state. Failure of the police to follow proper procedures may entitle you to suppression of your BAC results and help in plea negotiations.