Texans arrested for drunken driving should be prepared to give blood this holiday season.

Cities and counties across the state are increasingly demanding that drunken-driving suspects who refuse to take Breathalyzer tests submit to blood tests that measure the amount of alcohol in their systems.

The blood-test policy -- dubbed "no refusal" by law enforcement officials, because it prevents drivers from refusing to provide evidence of intoxication -- has grown from a novel procedure used in a few Texas jurisdictions to an initiative used by police statewide, particularly during weekends and holidays when drunken driving is most common. The no-refusal initiative has also caught on in other states, including Florida, Illinois, Louisiana and Missouri.

The attraction for law enforcement and prosecutors is that blood evidence is a powerful tool in front of juries. Armed with blood evidence of intoxication, prosecutors can win convictions in more than 90 percent of drunk-driving cases, said Houston police Capt. Carl Driskell, who works in the traffic enforcement division.

And often, lawyers say, defendants faced with blood evidence admit their guilt and don't bother with a trial. "If it bleeds, it pleads," said Fort Worth prosecutor Richard Alpert.

Texas courts have uniformly upheld the constitutionality of mandatory blood testing, attorneys said. But criminal-defense lawyers say such mandatory tests trample suspects' rights to be free from unreasonable searches and seizures.

"It's an erosion of civil liberties," said Austin defense lawyer Samuel Bassett. "If we can poke people involuntarily for evidence, where do we draw the line?"

The use of blood tests to measure a suspect's blood-alcohol content isn't new, but these no-refusal initiatives generally streamline the process by having magistrate judges standing by at a police station or other location to issue the needed search warrant. If the warrant is granted, nurses or other medical professionals are at the ready to draw blood. Police are empowered to strap a suspect to a chair, if necessary, to obtain a blood sample. That allows blood to be drawn quickly -- a key benefit to prosecutors because blood-alcohol concentrations dissipate over time.

"With no refusal, you don't have to go tromp down to the police station and then to a judge's house and then to a hospital, because you have everyone in one central location," said Warren Diepraam, a prosecutor in Montgomery County, north of Houston, which has a no-refusal campaign in place from Thanksgiving through New Year's.

San Antonio defense lawyer Jamie Balagia, a former police officer who now bills himself as the DWI Dude, voiced concern that magistrate judges involved in no-refusal campaigns may be prone to rubber-stamp search warrants. "There needs to be more transparency," Balagia said.

Over the July 4 weekend, almost 500 law enforcement agencies in Texas participated in a no-refusal campaign that netted about 1,500 DWI (driving while intoxicated) arrests. Bexar County, which includes San Antonio, recently implemented mandatory blood testing year-round.

In El Paso, police find that the policy actually encourages people to submit to breath tests. "We give people the option of blowing into a tube or getting poked with a needle," said Lt. Rod Liston. "People increasingly are going with the less painful option."

Police can't require breath tests for the simple reason that they can't physically compel someone to breathe out into a tube sufficiently to complete the test. So prosecutors bringing DWI cases sometimes have to rely on officers' eyewitness testimony, which they say often isn't enough to impress jurors accustomed to television crime dramas that feature cutting-edge forensic evidence.

"It's the CSI effect," said Bexar County District Attorney Susan Reed, referring to the popular television show about crime-scene investigators.

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