Rising blood alcohol concentration (BAC) and retrograde extrapolation are concepts related to the timing and measurement of alcohol in the bloodstream. They can play a significant role in DUI defense strategies.
A deeper understanding of these terms can provide essential context for applying them in the courtroom.
Understanding rising BAC
Rising blood alcohol concentration, or rising BAC, refers to the period during which alcohol absorbed into the bloodstream causes the BAC to increase. After consumption, alcohol doesn’t instantly reach its peak level in the bloodstream. It may take anywhere from 30 minutes to two hours for alcohol to be fully absorbed, so an individual’s BAC could continue to rise even after they’ve stopped drinking.
The rising BAC defense could potentially be used if the defendant’s BAC was below the legal limit while they were driving but increased to above the limit by the time they were tested. This could occur if the alcohol was still being absorbed into their system between the time of driving and the time of testing.
The role of retrograde extrapolation
Retrograde extrapolation is a scientific method used to estimate a person’s BAC at a specific time based on a later BAC test. This process involves taking the known BAC at the time of testing and working backward to determine the likely BAC at the time of the alleged offense. To accurately perform retrograde extrapolation, various factors must be considered, such as the time and quantity of the last drink, the period over which alcohol was consumed and the individual’s metabolic rate for alcohol.
Challenging the accuracy of a retrograde extrapolation might be possible if it’s believed that relevant factors weren’t adequately considered or if the methodology wasn’t correctly applied. For instance, if a substantial amount of time elapsed between the traffic stop and the BAC test, the defense could argue that the retrograde extrapolation is unreliable due to the numerous variables at play.
Both rising BAC and retrograde extrapolation defenses hinge on the idea that BAC levels fluctuate over time and that testing may not accurately reflect a person’s BAC when driving. If you’ve recently been accused of impaired driving, seeking legal guidance can help you to determine if these are viable options for your case.