Preview of Member Only Content
For full access: or Become a Member
Retrograde Extrapolation: A Scientifically Flawed Procedure (DWI)
By Dominick A. Labianca, Ph.D.
Retrograde Extrapolation: A Scientifically Flawed Procedure
If a driver’s blood-alcohol concentration (BAC) is below the legal limit when the driver gives a breath or blood sample, this fact will not stop the prosecution from trying to obtain a DWI conviction. At trial, the state may attempt to use retrograde extrapolation to convince the jury that the BAC exceeded the legal limit earlier when the police stopped the driver on the highway. But retrograde extrapolation is an unreliable tool.
According to the concept of retrograde extrapolation, a blood-alcohol concentration derived from the analysis of a subject’s breath or blood sample at a particular test time1 can be extrapolated back to the supposedly higher BAC existing at an earlier incident time. This is accomplished by adding to the BAC at test time the product of the hourly rate of alcohol elimination from blood (commonly termed the β value, as per Widmark2) and the number of hours elapsed between incident and tes
Want to read more?
The Champion archive is reserved for NACDL members.
NACDL members, please login to read the rest of this article.
Not a member? Join now.
Or click here to see an overview of NACDL Member benefits.
See what NACDL members say about us.
To read the current issue of The Champion in its entirety, click here.
- Media inquiries: Contact NACDL's Director of Public Affairs & Communications Ivan J. Dominguez at 202-465-7662 or firstname.lastname@example.org
- Academic Requests: Full articles of The Champion Magazine are available for academic and research purposes in the WestLaw and LexisNexis databases.