Dallas DWI Lawyer

CHEMICAL TESTS in a DWI
(Breath, Blood, Urine)

The State has the burden of proving a
Defendant is guilty of a DWI. If using a
chemical test, they must prove they are
above 0.08.

Consent needed: By law, a person can
refuse all tests requested by the police. The
consent to take a test must be shown to be
voluntary.

The State has the burden to show by "clear
and convincing" evidence that the test was
voluntary. Things the Court consider are:
1) if the police claim authority, 2) show of
force / coercive surroundings, 3) threatening
to seek / obtain a search warrant, 4)
deception of identity / purpose, 5) prior
unlawful police action, 6) if Miranda
warnings given, 7) if defendant was aware of
Fourth Amendment rights, 8) confessions or
other cooperation, 9) denial of guilt, 10)
defendant's maturity, sophistication, and
emotional or mental state.

Mandatory Specimens:
A police officer MAY force a person to take a
blood or breath test if they are arrested for a
DWI involving a death or serious injury
accident.

1) Breath Tests:
Most tests are done with Breath tests.
To be admissible, the State must 1) use
proper compounded chemicals in the
machines reference solution, 2) conduct
periodic supervision with someone who is
trained in the science of the machine, 3)
provide a witness to the test, so its
admissible, 4) prove certification of the test
operator, 5) prove that the breath's chemical
analysis was done pursuant to DPS rules.

2) Blood Tests:
The most accurate test is the blood test. To
be admissible, a blood test must: 1) show
the blood was taken by order or request of a
peace officer, 2) show the defendant's
consent, 3) the blood was withdrawn by a
proper person, 4) a sanitary place was used
to withdraw the blood, 5) inspection
periodically of the place where the blood
was taken.

3) Urine Tests:
The least reliable tests are Urine tests. They
measure the alcohol in the urine, which
means that if a person hasn't emptied their
bladder in several hours, the test may show
results of the alcohol content of that person
several hours before they were driving. For
the test to be valid, the officer just request
the person urinate 15-20 minutes prior to
the test. If not done, the test can be
successfully challenged.