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Forensic Uncertainty and Drunk Driving

Clarkston Legal July 9, 2016

“Doubt is not a pleasant condition, but certainty is absurd.” –Voltaire This post asks, from a forensic standpoint, just how sure are you, Mr. Prosecutor, about your evidence to support that drunk driving charge?

Reaching the Legal Limit

Imagine you are pulled over on suspicion of drunk driving. The officer at the scene administers a preliminary breath test which registers a breath sample containing alcohol in an amount high enough for the officer to arrest you and take you to the station for a Datamaster Breathalyzer Test or, if you refuse, a blood test.

Blood Alcohol Testing

If the results of the chemical breath or blood test show the concentration of blood alcohol exceeds the legal limit, then the prosecutor uses the as evidence of your illegal blood alcohol. If convicted you risk incarceration. Not only is your license suspended with 6-points added to your driving record, the assessment of fines, costs, and fees can reach the thousands.

It looks like the prosecution has the goods on you. Immediately, you are treated like a criminal.

On the other hand, some evidence -based on flawed or misapplied scientific principles- is inadmissible in court. Assume the chemical test results say you were “over the legal limit”. What if the test failed to properly consider was the “uncertainty” inherent in the measurement process?

Forensic Uncertainty

Forensic uncertainty is a scientific principle that holds that no scientific measurement can be 100% accurate, 100% of the time. In the case of the Breathalyzer, unexplained false positives mar the accuracy rate of the machine; lawyers have literally taken the Datamaster apart in trials, highlighting its every flaw. Failing to properly account for this uncertainty opens the test results to effective cross-examination in drunk driving cases.

For years, judges and prosecutors ignored this inconvenient scientific principle while exercising complete reliance on the test results touting 100% accuracy. Recently, those sands have shifted. Today, scientifically acceptable chemical testing for must contain some “uncertainty budget” to account for potential inaccuracy of the result.

Judges and defense lawyers now are better informed about the uncertainties of breath and blood test results. Courts have challenged the Michigan State Police Crime Laboratory on their testing techniques and the reliability of those results. For years, the lab touted idea that their results were 100% reliable; a scientific impossibility.

Further, the crime lab asserts that any uncertainty budget would be artificial. Recently, a judge in Mason County, threw out the prosecution’s blood alcohol test as too unreliable and thus inadmissible. The expert witness’s reliance on so-called “perfect” testing procedures and results formed the basis of the judge’s ruling to preclude the evidence.

Recent Example of Incorrect Analysis in State Crime Lab

This summer, the MSP reported incorrect analysis in over 4000 blood alcohol tests. The MSP informed state prosecutors that the thousands of suspect tests utilized an “incorrect calibration model” over a 4-month period. [Although this flaw does not involve the datamaster devices, the MSP’s forensic science division, the same division responsible for calibrating datamasters, announced the botched tests.]

While some of the flawed test results withstood scrutiny, more than half did not. This brings into question any drunk driving or illegal substance conviction resulting from one of the thousands of flawed blood test results.

The Criminal Defense Bar Responds

Responsible defense attorneys are knowledgeable about forensic uncertainty. As a result, the MSP has altered their results to include an uncertainty budget in breath and blood tests. However, many questions remain about the uncertainty budget calculation.

Criminal defense lawyers have been calling for an independent investigation of the MSP’s crime lab. First, any such investigation should focus on datamaster maintenance and calibration. Second, an investigation must examine the blood sample collection process. Third, the investigation should examine how those samples are used to obtain drunk driving convictions.

The recent admissions from the MSP crime lab’s forensic unit is more evidence supporting a long-held theory among criminal defense lawyers: the lab used flawed processes. Some convicted defendants are appealing.

The Uncertainty Budget

The MSP released data showing breath testing for uncertainty on only a handful of Datamaster machines. None of those machines have been in use in the field.

The uncertainty budgets ignored differing biological factors among individuals. Scientists believe such differences make-up more than 70% of an overall uncertainty budget.

The crime lab’s uncertainty budget fails to consider nearly three-quarters of the weighted factors that could contribute to an inaccurate result. This implies that the MSP is looking to appease the judges who challenged their supposedly infallible results.

Free Consultation

Finally, time is of the essence in all criminal prosecutions; before and after conviction. Consequently, if charged with drunk driving, contact our law firm for a free consultation to discuss your options.

Related Posts:

Debunking Junk Science

Proof Negative: NYT Magazine Article