1,000 DWI / DUI / drunk driving cases in Snohomish County Washington could be gutted in the latest battle defense attorneys are waging over the state toxicology lab’s scientific tests used to measure blood and breath alcohol levels.

Snohomish County District Court Judge Jeffrey Goodwin heard a full day of testimony Monday as defense attorney Ted Vosk argued that the state toxicology lab should calculate the margin of error for tests and those results should be provided to defendants and jurors.

There is a level of uncertainty for any scientific testing, Vosk argued. Test results can be affected by the measuring instruments, the materials being tested and numerous other factors. Jurors should hear the margin of error so they know that the results being provided are not absolute, that, in fact, alcohol levels could be lower than reported, Vosk said.

“All we’re asking is that this information be given to defendants and to the jury,” he said.

People’s lives are significantly impacted by a drunken-driving conviction, Vosk said.

If prosecutors are going to use these tests as evidence, they should be required to show the jury the full picture, the Bellevue lawyer said.

Last year county prosecutors filed nearly 3,000 drunken driving cases and 2,513 included breath-alcohol test results.

Prosecutors argue that the law doesn’t require them to provide an uncertainty calculation for each test. State legislators already have established the hurdles that must be cleared for prosecutors to introduce test results as evidence — a move to clarify drunken-driving law. The margin of error is not among the criteria, Snohomish County deputy prosecutor Elise Deschenes said.

Jurors should be allowed to hear the results even if the margin of error isn’t calculated. It is up to the defense attorneys to attack the results, she said.

“It’s just one more way that the defense attorneys are trying to keep out the breath tests,” Deschenes said.

Vosk relied on testimony from Ashley Emery, a University of Washington professor in mechanical engineering. He also is an expert in metrology — the science of measurement. Emery testified that without knowing the uncertainty of any scientific measurement, a person cannot draw any scientific conclusion about the number provided. Without knowing the margin of error, the result can be misconstrued and someone can draw the wrong conclusion, Emery said.

That is a standard understanding in science, he said.

“A defendant shouldn’t have to prove he’s innocent. It’s the state’s burden to prove” that the results are valid, Vosk said.

Deschenes argued that uncertainty calculations are new to the forensic sciences and aren’t standard in the field of breath and blood alcohol testing.

The state toxicology lab is ahead of the curve by being able to calculate the uncertainty of breath alcohol measurements, and it provides that information upon request, Deschenes said. It cannot yet calculate the margin of error for alcohol in blood tests.

Washington’s toxicology lab is among only three in the country that are accredited in the calibration of breath alcohol measuring instruments. It is not a simple process to calculate the margin of error, she said.

The Lynnwood courtroom on Monday was packed with defense attorneys from around the Puget Sound region, police chiefs from around Snohomish County and deputy prosecutors.

Goodwin did not make a ruling Monday, nor did he say when he expects to announce his decision.

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