Blood Tests Ruled Inadmissible Because Margin of Error Not Disclosed

Forensic science is an ongoing battleground for compelling evidence in criminal cases. Chemical tests, such as blood, urine and breath tests, are often the most useful pieces of evidence in the prosecution's case. Defense attorneys who successfully challenge the reliability of scientific tests can create enough reasonable doubt to merit an acquittal, or in some cases, obtain a dismissal.

During a recent drunk driving case in Mason County, the court ruled that blood test results offered by the prosecution were inadmissible since the crime lab that administered the tests did not report a margin of error. Speaking to the Lansing State Journal, the defense attorney explained that there are no absolutes in science, and that the judge made the correct ruling in excluding the test results. The attorney also noted that uncertainties in the collection and analysis of blood samples, as well as the reporting process, can create a range of possible results.

Also, the crime lab's chief toxicologist testified that a margin of error is not considered in determining blood alcohol levels in drunk driving cases. However, this could be crucial in close cases. Like many states, a person can be found guilty of driving under the influence with a blood alcohol level of 0.08 or above. A blood test showing 0.93, for example, could be subject to a 0.20 margin of error and may not be reliable because of the possibility that the defendant's BAC was actually 0.73.

While the ruling will have limited application for now, it could be expanded if the Court of Appeals or state Supreme Court rules on the issue. Should the ruling's application be expanded, blood test results would have to include information regarding the margin of error in order to be admissible.

In the meantime, an experienced attorney can help you understand your right to challenge blood test results if you have been charged with OWI.