A court looks at BAC assumptions that aren’t based on scientific investigation

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If only bitemarkers could be taken to task by a trial court like this blood alcohol ‘expert.’

On cross-examination, Wetstein [the BAC guy for the DA] acknowledged that he did not know what the defendant had eaten that night, how long she had been drinking, or what type of alcohol she consumed. Wetstein admitted that he did not attempt to determine when the defendant had entered the elimination phase, but rather assumed that she was in the elimination phase at 9:10 p.m. Wetstein explained that if a person had not consumed any alcohol since 7:30 p.m., he would be “quite confident” that the person was in the elimination phase by 9:10 p.m.

The appellate court reversed, finding that the expert’s opinion was improperly admitted. “A retrograde extrapolation calculation based on a single breath test, and when many of the factors necessary to determine whether the defendant was in the elimination phase are unknown, is insufficient to provide a reliable calculation and invites the jury to determine guilt on an improper basis. Based on the specific circumstances presented in this case, we believe that the prejudicial effect of the retrograde extrapolation calculation substantially outweighed its probative value and that the trial court abused its discretion in admitting it.”

  1. People v. Floyd, 2014 IL App (2d) 120507, 1-2, 11 N.E.3d 335, 336

About csidds

Dr. Michael Bowers is a long time forensic consultant in the US and international court systems.
This entry was posted in forensic science reform protecting the innocent and tagged , . Bookmark the permalink.

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