For years, one number has been hammered over and over in your head as well as those of every other driver in Columbus: 0.08. That is the percentage of blood alcohol content that law enforcement uses to determine whether or not you are legally drunk. Most hold to that number as the standard for alcohol content testing, yet as it turns out, there are other legal limits out there that you likely know little about. 

For example, were you aware that there are different forms of blood testing? When referring to the 0.08 standard, law enforcement officials are describing whole blood testing. Whole blood consists of a number of components, including: 

  • Plasma
  • Fibrinogen 
  • Cellular material 

When a medical blood draw is conducted, it is typically considered a qualitative test (yes or no). To make it easier to identify the presence of alcohol, samples are centrifuged to separate the solid components, which consists of the cellular material and clotting agents (fibrinogen) from the liquid (plasma). The liquid is then tested for alcohol. The trouble here is that by removing the solid components, what is left is a smaller liquid sample with the same alcohol concentration. This often produces higher results (as much as 16 percent, according to some experts). When using blood testing for forensic purposes, law enforcement officials are interested in quantitative (how much) as opposed to qualitative results. 

The law takes this discrepancy into account. According to the Ohio State Bar Association, the legal limit for blood serum or plasma is 0.096. Urine concentrations also have a different legal limit. As the sample mediums differ (yet the compound measured is the same), the state considers the legal limit for urine to be 0.11. It may be easy to see from these different test methods and limits why chemical testing results are often challenged.