A police officer is required to have reasonable suspicion of unlawful conduct in order to stop a driver (this is a lower standard than the probable cause needed for an arrest). Grounds for reasonable suspicion can vary, although reasonable suspicion is usually made in reference to a criminal or traffic statute. Your Houston DWI lawyer can analyze your case and determine whether law enforcement had an adequate justification to stop your vehicle.
The first thing to determine in a DWI case when examining whether a traffic stop was legal or not is whether the officer directly observed a violation of a law. There are circumstances where a police officer does not have to personally see a violation of the law in order to pull over a car, but the majority of stops made on the suspicion of DWI are justified by the office in question with a claim of direct observation.
It is important to remember that not all traffic violations justify a traffic stop. Courts have held that it is not reasonable to pull over a motorist only to check license and registration. In Texas, it is also usually not legal to stop a motorist for things like minor swerving in a lane, without first showing that the motorist somehow presented a danger to someone. Any stop made solely on these grounds might not be legal or valid, and as a result, cannot be the basis for a DWI investigation or arrest.
If your attorney can prove in court that the grounds for the stop were not legally sufficient, that could lead to evidence being suppressed. The suppression of evidence in a DWI case or other criminal matter will often lead to a dismissal of the charges against you.