There are several plausible issues to raise in any DWI arrest and case. While this list of DWI defenses is not complete, it provides a good start at Texas DWI defenses.
In order for law enforcement to pull over a vehicle, the officer must have a reasonable suspicion there is criminal activity afoot. In DWI context this generally means a traffic violation has occurred, meaning the officer has observed the driver breaking one of the traffic laws. Typically an officer will observe speeding, swerving, crossing road lines, or driving on the shoulder when pulling over a car for suspected DWI. The police report written by the officer will set fourth any reasonable suspicions as well as probable cause if the driver is arrested on DWI.
The legality of the traffic stop, in other words whether the officer properly judged both reasonable suspicion and probable cause could be challenged in court by a motion to dismiss. If the district attorney cannon show the traffic stop was valid then the case should be dismissed.
In a DWI arrest, the district attorney must show the vehicle was moving and operated at the time the driver was intoxicated above the legal limit. Operating the vehicle means the driver must have actual control over and manage the cars movement.
Some DWI cases may present a peculiar set of circumstances concerning operating a motor vehicle. Often times, an individual leaves a bar and will sit in their car-- often intending to sleep there rather than drive. In such a scenario the individual could not be said to be operating a car under the DWI law. Officers observing this behavior may arrest for DWI however the district attorney would need to prove the driver was operating the car, not merely sitting in it.
Law enforcement must conduct their investigation within the limits of the law. If an officer uses illegal procedures in order to search or obtain confession, the violation of an individuals right can serve as a basis for a motion to suppress. One of the more common violations is the failure to read Miranda rights to a person arrested and being questioned. While successful motions to dismiss may not get the case dismissed, they will limit and prohibit the jury from hearing evidence obtained in violation of your rights.
Just like law enforcement officers, District Attorney's must also take care not to violate your rights in a criminal trial, particularly when disclosing discovery and evidence in a timely manner. The DA must provide to defense all of the evidence he or she intends to use at trial with which they will attempt to prove guilt. This means if the DA attempts to use evidence not handed over to defense, or violates discovery rules and laws, the evidence -- even if obtained legally -- may be suppressed or excluded.
A machine is only as good as the people making it. In every day life, our machines fail time and time again, be it our computers, phones, or even televisions. It stands to reason that a breath-testing device, commonly referred to as a Breathalyzer test, is also subject to the same mechanical failures and inaccuracies. Specifically, breath test machines must be properly calibrated and checked frequently in order to maintain accuracy. If the technician working on the Breathalyzer missed calibration by a small amount, the testing for that device will be incorrect. Likewise, the breath test is a method to gauge blood alcohol levels (BAC) at the time of driving. Therefore, a breath test given two hours after driving will not accurately show the driver's BAC or alcohol levels at the time of driving. Only after several mathematical calculations can a lab technician attempt to ballpark the alcohol levels at the time of driving based on the breath test.
Tests conducted at the officer's request, typically within minutes of being pulled over for a DWI stop, are called field sobriety tests. Generally consisting of physical feats like the Walk and Turn, Stand and Pat, Counting with Eyes Closed, and the One Leg Stand. Other field sobriety tests or FSTs are the Horizontal Gaze Nystagmus, or HGN, and the Finger to Nose test.
These tests are completely subjective for the officer conducting them; he or she is looking for mistakes in order to note them for later use in court. They are NOT marking down what you did correctly, only what you fail o have trouble with. Many people have physical issues such as age, illness, handicaps, back or knee problems, or feet issues that would inhibit free movement, meaning those individuals will fail the test, regardless of alcohol level.
FSTs are for the most part flawed when attempting to decipher whether a person is intoxicated. Several studies, including the National Highway Traffic Safety Administration (NHSTA), have concluded that out of all the field sobriety tests, only three seems to have any correlation to gauging intoxication and DWI: HGN tests, walk and turn, and one leg stand, however the highest accuracy percentage of the three tests was found to be 77% -- meaning that nearly 1/3 of the time, the test yields inaccurate results.
Observations of officers are subject to cross-examination in court, such as smelling alcohol, driving, fumbling with paperwork or license, and stumbling or slurred speech. These observations can be challenged in a variety of ways.
There are just a few of the typical methods to challenge a DWI case and defend against DWI charges. Some may not be applicable in every case, however, so it is best to speak with an attorney concerning your DWI case.