Idaho man claimed he wasn’t driving drunk. Judge erred by not allowing him to argue that.

The Idaho Supreme Court on Tuesday sided with an Ada County man who tried unsuccessfully to argue he wasn’t driving drunk when he was stopped by an Ada County sheriff’s deputy in April 2015, overturning his conviction.

Justin Keith Austin, now 47, said he drank three alcoholic beverages in rapid succession before getting into his car and driving. Austin sought to introduce expert testimony claiming that his blood alcohol level rose during the 35 minutes between the time he was pulled over and when Deputy Brian Richardson conducted two breath tests.

The tests showed Austin’s blood alcohol level at 0.085 percent and 0.086 percent, above the 0.08 percent that constitutes driving under the influence under Idaho law. The tests were administered after Richardson administered field sobriety tests, which he said Austin failed.

At trial, Austin sought testimony from Loring Beals, a clinical toxicologist, who was prepared to testify that he felt Austin’s blood alcohol level had increased while he was waiting for the breath tests to be given.

“Based on his gender, height and weight, I calculate that at the time was was stopped, his alcohol concentration would have been around .06 (percent) to .065, rising to the higher level by the time he was actually tested a half-hour later,” Beals wrote in a latter referenced by the Supreme Court.

Prosecutors argued that the argument was irrelevant. They said Idaho law established a driver’s blood alcohol level at the time the test was administered and that they did not have to prove the relationship between that level and what it may have been at the time a driver was pulled over for impaired driving.

Ada County District Judge Michael Reardon agreed with the prosecution and excluded the testimony. A jury convicted Austin of felony driving under the influence. He was sentenced to 90 days in jail, with 60 days suspended, and placed on probation for seven years.

In a ruling issued two days after Austin was arrested, the Idaho Court of Appeals said “the state is not required to extrapolate the result of an evidentiary test — whether it be for blood, breath, or urine — back to a time when the defendant was driving.” It even went so far to say the blood alcohol level at the time a defendant was behind the wheel was irrelevant.

Austin argued that the prohibition against presenting any extrapolation evidence to defend against a DUI charge violated his due process rights.

In a six-page decision authored by Justice Robin Brody, the Supreme Court found that the Court of Appeals erred in allowing the test results to show a driver was above the legal limit without allowing the defense to challenge the assertion.

The court overturned Austin’s conviction and sent the case back to district court.

John Sowell: 208-377-6423, @JohnWSowell