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Blood Tests

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After a driver has been placed under arrest for DUI, the driver will be informed that per California’s implied consent law, the driver must submit to a breath or blood test.  In this article we will examine the blood test.

What is implied consent?

California’s implied consent law requires that any driver, whether a resident or non-resident, who has been arrested for DUI, submit to a chemical test, either a breath or blood test, to determine the driver’s level of alcohol concentration.


If a person refuses the chemical test, the driver will face increased DUI penalties as well as a mandatory driver’s license suspension regardless of the outcome of the case, including if the case is dismissed.  If you are found guilty, you may be subject to additional time in custody.

Blood or breath test?

We are often asked whether it is better to take a blood or a breath test. The choice is entirely up to you but there are advantages to both.  In the case of a blood test, the advantage comes from the ability to have the blood retested by your own lab.  Blood test also measure the exact amount of alcohol in your blood, while the breath test measures deep lung air and then converts this into a blood alcohol level using a formula. 

Blood draw procedure

After you are arrested and you choose a blood test, the police are going to transport you to either the local hospital or the police station.  At either location, the police will have a licensed phlebotomist come and conduct the blood draw.  The phlebotomist follows a strict procedure with each blood draw.

First, the phlebotomist is supposed to use a new and unopened kit.  Inside this kit it everything the phlebotomist needs to conduct the blood draw.  Once the kit is open, the phlebotomist will apply a venous tourniquet to make your vein pop more.  The phlebotomist will then clean the needle site with a non-alcoholic swap designed specifically for blood draws.  The phlebotomist will then draw a couple vials of blood.  These are then turned over to police as part of the “chain of custody”.

Can I refuse a blood test?

Yes. You can refuse to take a blood test and instead elect to take a breath test or a urine test if its available.  However, you are required to choose a chemical test. If you refuse, or try to delay the chemical test, the police will treat this as a refusal, and they will seek a blood draw warrant. In almost every case where a blood draw warrant is sought it will be granted.  The police officer will sign an affidavit regarding their observations at the scene, including any field sobriety tests you performed, and they will note your refusal.  Every county has a judge that is on-call for warrants during the night and in most counties, there is a “backup” judge should the first one be out of reach.


Once the police obtain the warrant, you will be advised that if you refuse and resist, the police will force the blood draw if necessary, including holding you down while the blood draw is conducted.  The police will also note the forced blood draw in the police report.  The district attorney will likely then charge a DUI refusal enhancement and use the evidence of the forced blood draw at trial as proof that you knew you were driving under the influence under.

Challenging a blood draw

There are a few ways that an experienced defense attorney can challenge the blood draw and the result of the blood testing.

Initial Blood Collection

One of the ways a DUI blood draw can be challenged is attacking the initial collection itself.  As mentioned, the phlebotomist is supposed to use an unopen kit and swab the area with an alcohol-free swipe. However, this procedure is not always followed.  If the phlebotomist is busy or has a number of other blood draws to get to (many organizations use a company where the phlebotomist travels to police stations) they make mistakes.  In another aspect to the collection process, the vials the phlebotomist use are required to contain a certain amount of preservative. If they don’t, the blood itself will ferment and actually increase its alcohol level. By having the blood tested by your own lab, the analyst will be able to tell if the proper amount of preservative was used and what effects the lack of preservative had on the blood sample.


Real Life Example: Phlebotomist ran out of alcohol-free swabs and was in a rush.  Officer provided phlebotomist a swab from the station first-aid kit. It was later determined the swab used contained 2% ethanol.  The defense argued the blood results were therefore tainted to the point the judge said the blood would be inadmissible if case went to trial.


Chain of Custody


Once the phlebotomist draws your blood, they will turn it over to the police to maintain the “chain of custody”. The chain of custody refers to the ability to track evidence at every stage. This ensures that the evidence was maintained appropriately. However, the chain of custody is prone to human error.  There are times when evidence may be lost, switched, or mislabeled.  An experienced DUI attorney, especially one who had the responsibility as a prosecutor to maintain the chain of custody, knows how to attack the chain.  A lapse in the chain of custody does not mean the results will be inadmissible, but it can help to greatly damage the prosecutor’s case and force a plea deal or even a dismissal.


Real Life Example: A defendant was arrested for DUI and had her blood drawn. The phlebotomist provided the blood to the officer. The officer then received a priority call while transporting the blood. The officer then forgot about the blood in the truck of the patrol car until he returned to work three days later.  Using the chain of custody logs, the defense was able to show that the blood had an unaccounted period of almost four days.  The chain of custody was so tainted that the prosecution chose to dismiss the case.

Time Frame


Another way to attack a blood result is to attack the timeline.  While breath samples taken at the scene of the arrest and then relatively quickly at the police station, blood results can be hours after the arrest.  The police must transport you to the hospital or police station. They must then wait for the phlebotomist to show up and conduct the blood draw. In that period, your blood results can change drastically based upon when you last consumed alcohol, when you last ate, and factors related to you personally.  By attacking the time frame, the criminalist will have to admit that its possible your blood could have been a different level at the time you were driving.


Real Life Example: A defendant consumed a couple of drinks prior to leaving a bar.  Prior to leaving, the defendant downed his last beer.  Defendant was stopped within ten minutes from leaving the bar and arrested for DUI.  By the time the phlebotomist arrived on a busy night, the defendant has been waiting over an hour and a half.  The defense was able to show that at the time the defendant was driving, his BAC was below the legal limit and that his blood level was only about .08% because he had to wait almost two hours by the time everything was completed

Dedicated DUI Attorney

Kevin Ballard is a dedicated DUI attorney based in Fairfield who understands how to effectively defend those charged with DUIs. Kevin is one of the few attorneys who is both a former prosecutor and trained as a police officer. As such, Kevin knows first hand how DUIs are handled from the initial traffic stop through prosecution and appeal. Let the Law Office of Kevin L. Ballard help you today defend your rights and protect your liberty.

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