How Accurate Are Breath Tests In Determining Alcohol Impairment?

Attorney Myles Berman explains let’s first talk about breath testing both pre-arrest and post-arrest. The pre-arrest breath tests are administered when the person is still being investigated. A lot of times on the street they will give another evidentiary post-arrest breath test n the same machine or on the same type of machine, a portable handheld breath test machine. Also, after somebody is arrested for a DUI, they are taken to jail and administered breath tests on big desktop machines but I am going to characterize both of these breath testing machines as breath testing in general. In my professional opinion, breath testing is not accurate at all to determine the alcohol level in a person’s blood. The first and obvious reason is that the breath test machines are measuring alcohol on a person’s breath, not alcohol in a person’s blood.

All breath testing machines in California are calibrated to assume that the relationship between the alcohol on a person’s breath and alcohol in their blood is the same. The ratio for breath and blood is always the same for all people at all time. That is called the partition ratio. But the ratio s set by statute and the legislature that incorporated this ratio into this statute was based on merely an average; not for all people at all times. So, let’s say a person is 6’5” and 300 lbs., all breath testing machines assume that the ratio between alcohol on that person’s breath and the person’s blood is the same as a 115 lbs. female and that is just not the case. To further prove my point the breath testing, more often than not, gives two different results within minutes apart. For example, a person can end up with a 0.16 and then a 0.18 two or five minutes apart.

It is scientifically impossible for a person to go from 0.16 to 0.18 in a span of 2 to 5 minutes. In California, breath tests consist of two separate breath samples. It is the same in reverse. If a person has a 0.20 breath test and shortly after that, 2 to 5 minutes later, has a 0.18 breath test, then that’s scientifically impossible for a person to go from 0.20 to a 0.18. The same is true if a 0.08 and a 0.11 and a 0.09. It’s just not accurate. Contact Top Gun DUI Defense Attorney Myles L. Berman serving clients throughout Southern California and he will represent you with the care and attention you expect.