The Supreme Court is considering whether police must get a warrant before ordering a blood test on an unwilling drunken-driving suspect.

The justices heard arguments Wednesday in a case involving a disputed blood test from Missouri. Police stopped a speeding, swerving car and the driver, who had two previous drunken-driving convictions, refused to submit to a breath test to measure the alcohol level in his body.

The justices appeared to struggle with whether the dissipation of alcohol in the blood over time is reason enough for police to call for a blood test without first getting a warrant.

In siding with defendant Tyler McNeely, the Missouri Supreme Court said police need a warrant to take a suspect's blood except when a delay could threaten a life or destroy potential evidence.