DUI and Blood Tests: Preparing the Sample

In a DUI blood case, the sample has to be prepared for testing. This is another area that an experienced Phoenix DUI attorney should look into for you.

First, the tube is removed from refrigeration and allowed to come to room temperature. Generally, the tube is placed in a rocker device that gently rocks the contents back and forth to ensure a good mix.

Once the sample is a room temperature, the top is removed. Then the contents are poured into a container. A measured amount is removed from this container via a pipette. This process should be controlled electronically rather than manually, to ensure accuracy and reliability. Pipettes can be checked for accuracy by drawing a known amount of distilled water and depositing it onto a scale to check its weight. Maintenance and calibration records should be available for the pipette.

The blood removed by the pipette is then transferred into a headspace vial. It is called a headspace vial because the testing device measures the alcohol in the headspace above the vial in the blood. Then a measured amount of internal standard is then added to the headspace vial. The internal standard and its purpose will be discussed in a later blog post. More sophisticated labs have pipettes that transfer the internal standard simultaneously with the blood; such a device is called an auto-dilutor, and it will have maintenance and calibration records which must be checked. The headspace vial is then crimp sealed; the quality of this seal is vital, as will be discussed later.

Two samples of blood from the same tube should be tested; the results should agree within 5%. This will be discussed more in a later blog post as well.

The pipette must be rinsed clean between samples to avoid cross-contamination from previous blood samples. Only de-ionized water should be used to rinse the pipettes. As will be discussed in a later blog post, the device which detects alcohol in the sample does so by counting the ions that hit it, and assumes that each ion represents alcohol; introducing additional ions, therefore, is obviously a bad idea.

The headspace vials from your tube, along with tubes from several other people, are then placed into an autosampler; this is an automated rack that which moves each vial into place for sampling. The autosampler also heats and shakes the vials to ensure proper mixing. The autosampler allows the lab to set up the machine to test a number of samples automatically, one after the other, without a lab tech having to be present to inject each sample. In fact, the lab tech will often set up a run of samples, turn the machine on, and leave for the day, allowing the samples to be tested automatically during the night.

If you have been charged with a DUI anywhere in the Phoenix area, contact us right away for a free consultation.