SEATTLE -- A suspected DUI driver's refusal to take a field sobriety test can be used against them in court, a deeply divided Washington state Supreme Court ruled Thursday. It's a significant victory for the police and prosecutors trying to crack down on DUIs.

The case stems from the 2011 arrest of Mark Tracy Mecham, who was pulled over for an outstanding warrant in King County. The arresting officer suspected Mecham of being impaired and asked him to take a field sobriety test, which involves walking a straight line, standing on one leg, and observing eye movements. Prosecutors said Mecham refused, and also refused several times to take a breath test when he was booked.

His refusal to take the field sobriety test was used as evidence at his trial, and he was convicted of DUI. The conviction was increased to a felony due to multiple previous convictions.

Mecham appealed, saying that field sobriety tests constitute an unreasonable search under the Fourth Amendment of the U.S. Constitution and Article 1, Section 7 of the Washington state Constitution.

In the 5-4 decision Thursday, the state Supreme Court ruled a suspect does not have a constitutional right to refuse field sobriety tests, and the tests are not considered a search under either constitution.

Of the four justices who dissented, two said Mecham's refusal to take the test was incorrectly treated in court as an admission of guilt. The other two justices said since Mecham was already under arrest, the test was purely a search for evidence and therefore unconstitutional. The dissenting justices said the case should be tried again.

One justice, Mary Fairhurst, concurred with the overall ruling but dissented on one aspect of the case.

Washington State Patrol Trooper Clark Jones says the tests play an important role in helping them keep the streets safe. "We like it when people submit to the test because it enables us to make a more accurate decision" Jones explained.

"With a high degree of accuracy, we're able to tell if someone is above the limit and we can tell if they're affected by alcohol."

Defense Attorney Francisco Duarte says he worries the court's decision will make it hard for people to get a fair trial. "They have the right to choose roadside testing or not and today's decision basically destroys the concept of voluntariness" he said.

Duarte says nobody should be behind the wheel if they're impaired, but he says some people refuse to take the test because of health problems or concerns about the process.
"The tests are designed to create imbalance and the results are misused and overstated" he explained.