An April Supreme Court ruling may render some Texas DWI laws unconstitutional and have an impact on future DWI investigations.

Missouri v. McNeely revolved around a DWI suspect who refused a blood test. The Missouri man was stopped by a state trooper for speeding on a rural road. He failed several field sobriety tests. Despite refusing the test, blood was taken anyway, without a warrant being obtained.

The driver was transported to the hospital and handcuffed while a technician drew his blood. The blood-alcohol level was 0.154 percent, almost two times the legal limit in the state.

The Supreme Court majority opinion in the case concluded that the fact that blood-alcohol levels dissipate over time does not create an “exigent circumstance” that would allow police to take blood in every case without a warrant.

“In some circumstances, law enforcement officers may conduct a search without a warrant to prevent the imminent destruction of evidence,” Justice Sonia Sotomayor wrote for the court. “In those drunk-driving investigations where police officers can reasonably obtain a warrant before a blood sample can be drawn without significantly undermining the efficacy of the search, the Fourth Amendment mandates that they do so.”

The ruling does not go so far as to mandate that a warrant is always needed, but will require that individual cases be judged on their own merit.

Several categories of DWI and other intoxication offenses in Texas are subject to “mandatory” blood draws. These include cases in which the accused has two prior convictions or there is an accident that injured someone.

Houston DWI lawyers know that Harris County’s “no refusal” program has rapidly increased the efficiency of obtaining warrants for blood draws, so this ruling may not hugely impact those arrested for DWI or DUI in the Houston area.