In this Sept. 11, 2009 photo, after reading the rights to an alleged extreme DUI suspect, Phoenix Police Department Officer James Lawler, of the DUI Squad, administers a blood test as he works out of a mobile DUI processing van in Phoenix. In a decision that defense attorneys said respects the Fourth Amendment, the Arizona Supreme Court ruled Monday that police must get a search warrant to take a blood sample from a DUI suspect unless the person clearly consents to providing a sample.

PHOENIX - Blood samples taken from motorists without their explicit on-the-spot consent can't be used to convict them of drunken driving, the Arizona Supreme Court ruled Monday.

The justices acknowledged Arizona has an "implied consent" law saying motorists agree to provide a sample of blood, breath or urine for testing if they are charged with driving under the influence of alcohol or drugs.

But Justice Scott Bales said police still need a warrant from a judge to draw blood without the driver's explicit approval.

Bales, writing for the unanimous court, said the "implied consent" law simply makes giving consent a condition of having an Arizona license. He said that allows motorists to refuse, with the understanding their licenses will be taken away, something that remains unchanged by this ruling.

Deputy Pima County Attorney Bruce Chalk said he does not think Monday's ruling will make it harder to convict suspected drunken drivers. Chalk said that if motorists balk, police still can obtain search warrants if they have probable cause to believe someone was driving while intoxicated.

The case involves the 2007 arrest of Jose Carillo by Phoenix police on charges of driving under the influence. He was taken to a nearby DUI van where testing was delayed because Carillo, sitting on the van's steps, was sick for about 30 minutes.

While Carillo was sitting there, one officer placed a large toolbox on Carillo's lap while another took a blood sample.

Carillo attempted to keep the results of the sample from being used at his trial. He testified he spoke only Spanish; the officers acknowledged they were not certified translators, they communicated through gestures and Carillo gave no resistance.

As a result, the city magistrate concluded nothing in Carillo's conduct indicated that he refused to consent to the test.

On appeal, city prosecutors argued that the wording of the implied-consent law shows approval is considered automatic, absent a specific rejection.

As proof, they noted that the law spells out that someone who is dead or unconscious is presumed not to have withdrawn consent. Based on that, they said if blood can legally be taken from an unconscious person, it also can be taken from someone who is merely silent.

Bales, however, said that's not the way the law works - at least not with those who are, in fact, conscious.

He pointed out the law requires police to ask a motorist to submit to a test and to inform anyone who refuses that doing so will result in loss of license. Bales said the law says that if a person refuses to submit, the test "shall not be given . . . unless pursuant to a search warrant."

The court also rejected arguments that requiring specific consent each time a test is sought undermines the state's drunken-driving laws.

"The key purpose of the implied-consent law is to remove from Arizona highways those drivers who may be a menace to themselves and others because of intoxication," Bales wrote.

"One way the Legislature chose to achieve this goal was by providing for the prompt suspension of the licenses of arrestees who refuse testing," the judge continued. "Rather than statutorily authorizing the warrantless administration of tests on such persons, the Legislature instead deemed a failure to expressly agree to be a refusal."

Bales said that refusal becomes the basis for summarily suspending the person's license.

Finally, Bales said the statute does require someone who is arrested to "expressly agree" to being tested without a warrant. He said that means "in direct or unmistakable terms and not merely implied or left to inference."