DUI Blood Testing in Montana: Behind The Scenes

If you’ve been arrested for a DUI in Montana, may have had your blood drawn by law enforcement. You probably think that the crime lab tests your blood for alcohol.

But you’d be wrong.

In today’s post we’ll take a behind the scenes look at what actually happens when blood is drawn as part of a Montana DUI investigation. Here at the Judnich Law Office our DUI defense attorneys are trained to understand the science behind blood testing as well as the proper testing procedure.

When representing clients in DUI cases, we look for variation from the standardized testing protocol. Remember, this is one of the only ways to exclude blood testing results from trial. Our attorneys spend more time, expense, and training on DUI investigation that any other Montana DUI lawyers.


Getting a warrant to draw your blood

Law enforcement can only obtain your blood through a search warrant or if you voluntarily consent to give it to them. A nurse or medical tech must draw your blood and put it into a special set of containers for law enforcement purposes to ensure proper preservative.

Special care must be kept by law enforcement and medical staff to ensure proper chain of custody, sealing of samples, and collection technique to comply with protocol.

The blood vials are then stored and transported to the crime lab in Missoula, Montana. At the crime lab, a tech will inspect the vials and open 1 of the 2 vials for testing. A very precise amount of the blood is removed from the 1 vial and placed into a testing vial. Enough blood is sampled to ensure there is air above the blood within the testing vial.

Here is where it gets interesting.


Your blood ISN’T tested…

A machine called a Gas Chromatograph with Flame Ionization Detector or (GCFID) will then start the process after a tech places some blood into a testing vial. In the machine a needle is mechanically inserted into the sealed vial and a measured amount of the air from the vial is removed — not the blood.

This air is called headspace, and under the physics principle of Henry’s Law, because ethanol alcohol is volatile, those alcohol molecules will have an equal proportion in the blood and in the sealed air above it.

So, the machine actually only tests the molecules in the air. It gets much more complicated from there, but that is the very basic short version of it. The machine then splits the sample into two separate tests that are independently tested for ethanol and other substances.


Once the machine has run the headspace sample through the chromatograph, the results are charted in both a printed out form called a Chromatogram and stored digitally.

Unfortunately, the government does not release the results of the Chromatogram to anyone without a court subpoena. Instead, the crime lab tech will look at the results and calculate an average of the 2 results, and then create a 1-page document which is essentially a summary of the testing results.

That 1-page summary is the only thing that the government usually voluntarily gives over to a person accused of DUI and usually the only actual evidence a jury sees of this entire process.


Human error…

Here’s the problem: Human error can occur in this process, resulting in mistakes in the final 1-page report. Further complicating the process is that access to the actual chromatogram results and comparison testing data from the machine is limited.

Yet this is the only way to fully evaluate the test result, and determine if the testing machine has any problems that can skew the results.


Who can help?

Only the very best and most experienced DUI defense attorneys truly understand this process, obtain the necessary information, and actually use that evidence to help defend someone accused of DUI in Montana.


DID YOU KNOW: Marty Judnich & Nathan Hulling are NHSTA certified DUI defense attorneys



DUI defense attorneys, Marty Judnich and Nathan Hulling are among the most credentialed and accomplished in all of Montana. There’s no other attorney who can give you a more comprehensive defense of your DUI charge — including the examination of blood draw evidence.


The team at the Judnich Law Office fights every day for this information and maintains cutting-edge training and education on these subjects to assist our clients.


Schedule your consultation

If you’ve been accused of DUI in Montana, we can help. Contact our DUI attorneys today for a free and confidential consultation.