Has anyone ever had both a blood test and a breathalyzer test taken? were the results different?

Question

If you have had both tests done by a police officer, please tell me what the results were and how far apart the tests were taken. I'm wondering about the accuracy of the breathalyzer test. My bf was drinking the other night. This one girl really needed a ride home and he was the only one who could give her one. He waited about an hour and tried sobering up and drinking a lot of water. He didn't want to drive so soon but he felt bad for her. Now please don't start going off on how dumb he is for drinking and driving because I know someone will but its pointless now... he rarely drinked to begin with and hes done drinking now. On the way there, my bf was pulled over because he needed some car repairs. He tested a 0.08 on the breathalyzer the first time. He passed a field sobriety test without any trouble. They cops had him sit around for like 15 minutes and had him take it again. The breathalyzer gave a reading of 0.09 the second time. They drew blood shortly after. I've been reading online about a margin of error with these breathalyzers. I wonder if the blood test could give different results. Also, my bf is a pretty big guy.. 6'3 260 pounds, so I'm wondering if a large body size could give a false positive on the breathalyzer test. If his blood test gives results under 0.08, hes off the hook without a DUI because the cops didn't report anything wrong with his driving and because he passed the field sobriety test. What are your experiences if you've had those tests done? Were the results different from each other?

Answer 1

PBT is the preliminary test, the breathalyzer is seperate.  Blood test is different.

Where I live, PBT is done at the stop, then breathalyzer at the station.  The breathalyzer is preferred since it is easy to use and is accurate / inexpensive.  Blood tests take more time and the samples need to be sent to the crime lab for processing.

Blood is taken when the subject is unconscious (think bad traffic accident) or when the subject requests in in lieu of the breathalyzer.

Typically, the blood test results will be a bit higher, depending on when the sample was taken and how much alcohol the test subject has in their system.

I predict that your boyfriends blood results will be around .095 or so.

(BTW - drinking lots of water doesn't help sober you up, it just makes you pee more)

Answer 2

The breath test given at the scene of the stop is actually a Preliminary Breath Test (PBT), and is not as accurate as a blood test. It is a screening tool only, and not admissible in court.

The 15 minute waiting period is common. The reason for this is if you just finished a drink, some alcohol remains in your mouth for up to 15 minutes before it is absorbed. This residual alcohol can give a higher reading. By taking two tests 15 minutes apart, you can confirm the test result is not from the residual mouth alcohol.

Because the PBT may only displays 2 digits, the two readings could be within 1/100th of one percent, for example 0.089 and 0.090.

As far as drinking lots of water, that will not sober you up any faster. The only thing that helps is time. His height and weight will not affect the test either.

I've given breath and blood tests 100s of times. From my experience, a blood test will normally be slightly higher than breath.