An appellate court has overturned a Carpentersville woman's fourth DUI conviction, ruling a prosecution witness's estimation of the woman's blood alcohol concentration was "inherently unreliable."
A jury in 2012 convicted Chrystal L. Floyd, 35, of the 100 block of Silverstone Drive, of aggravated DUI after she was arrested near the Dolphin Cove Family Aquatic Center.
Floyd's past criminal record, which also included burglary, required Judge Marmarie Kostelny to sentence Floyd to at least six years in prison.
Her sentence was cut in half for good behavior, and she was released from prison in January.
Floyd was arrested June 16, 2011, after police were called for a disturbance in the aquatic center's parking lot. She took a breath test at the police station at 10:30 p.m. that showed her blood alcohol content to be .069; the legal threshold in Illinois is .08.
During her trial, the expert's "retrograde extrapolation calculation" put her BAC between .082 and .095 at about 9:15 p.m. that night, the time of her arrest, according to the court's opinion.
In her appeal, Floyd's attorneys argued that the state's expert witness failed to consider other factors, such as how much she had eaten, what type of alcohol she had consumed, and when her body entered the "elimination phase" for processing alcohol. The appeals court agreed and reversed her conviction.
"Because the state's expert witness acknowledged that he was unaware of any factors necessary to determine whether defendant was in the elimination phase, and because police conducted only one BAC test, we find the extrapolation calculation to be inherently unreliable," the judges wrote.
"In addition, because the extrapolation evidence invited the jury to convict the defendant on the basis of supposedly high BAC, the potential for prejudice for admitting the evidence was high."
It was not immediately known if Floyd will be put on trial again.