The majority of DUI investigations hinge on the results of either a breath
or blood test after an arrest. While slurred speech and failed sobriety
tests can provide the evidence the court needs to secure a conviction,
the amount of alcohol in the driver’s system is the most important
proof. Sickness can cause you to slur your speech and a physical impairment
can result in an unsuccessful walk-and-turn test, yet there is no doubt
when your blood alcohol percentage is shown to be over .08%...or is there?
Challenging a Breath Test
Modern breathalyzers are reasonably accurate, but they’re prone to
mistakes and errors just like any other similar devices. All breath test
devices have a built-in margin of error that can be off by as much as
.01%. A driver who is just barely over the legal limit has a good argument
based on this margin of error, and the prosecution may not be able to
prove the charge beyond a reasonable doubt.
A contaminated breath sample can also cause a higher BAC reading than normal.
A breathalyzer is designed to measure the concentration of alcohol from
the vapor in your lungs, but to get an accurate measurement, no alcohol
can be in your mouth. If there is, the results are a combination of your
lung and mouth alcohol, which can significantly raise your actual BAC.
To avoid this issue, officers are supposed to observe a driver for a 15
to 20 minute period before administering a breath test. If an officer
doesn’t adhere to this waiting procedure, you may be able to raise
questions about the veracity of the results.
Challenging a Blood Test
Generally speaking, blood tests are more accurate than breath tests, but
that doesn’t mean they’re always correct. Below we’ll
go through several situations in which a blood test may be challenged:
Fermentation: One of the most common sources of errors during a blood test is improper
storage. If blood isn’t stored properly it can ferment, which can
increase the BAC in the sample.
Blood draw without a warrant: Police generally need a warrant to require a blood test. If they obtain
one without a warrant, the results could be thrown out.
Rising blood alcohol: A “rising-blood-alcohol” defense establishes a person’s
BAC was below the legal limit while driving, but rose by the time the
testing was conducted, since the body takes time to absorb alcohol.
If you have been arrested for DUI, contact our
Murrieta criminal defense lawyers at Hanson, Gorian, Bradford & Hanich today.
or contact us online.