What is retrograde extrapolation?
Retrograde extrapolation estimates a prior BAC from a later measured BAC by considering elapsed time, alcohol elimination, and whether the person was still absorbing alcohol.
Who uses DUI Professional?
Defense attorneys, prosecutors, forensic toxicologists, and expert witnesses use retrograde extrapolation tools to evaluate the relationship between driving time and testing time.
Make the assumptions visible
Retrograde extrapolation depends on elapsed time, elimination rate, drinking pattern, and absorption state. DUI Professional helps users document and compare those assumptions.
How the software supports review
Users can model a timeline, set keypoint times, adjust assumptions, and generate reports that show how scenario changes affect earlier BAC estimates.
- Earlier BAC estimate support
- Elapsed-time analysis
- Absorption versus elimination phase review
- Keypoint time comparison
- Scenario and report output
- Professional assumptions documentation
Frequently Asked Questions
When is retrograde extrapolation most sensitive?
It is especially sensitive when drinking continued near the driving time or when the absorption phase is uncertain.
Can the same test result support different conclusions?
Yes. Different assumptions about drinking history, absorption, and elimination can produce different earlier BAC estimates.
Does the software decide admissibility?
No. The software supports analysis; legal admissibility and expert foundation are handled by qualified professionals and the court.
Evaluate retrograde extrapolation assumptions
Use DUI Professional to test timelines, compare assumptions, and prepare better expert-review questions.
DUI Professional does not determine guilt, impairment, admissibility, or the legal sufficiency of evidence. It provides structured BAC scenario modeling and report support for qualified professional review. Legal conclusions and forensic opinions should be made by appropriately qualified professionals using case-specific facts, jurisdiction-specific law, and applicable scientific standards.
Sources
These references support the scientific and forensic context discussed on this page.
- ANSI/ASB Best Practice Recommendation 122, First Edition 2024 Current forensic alcohol calculation guidance for assumption-based alcohol calculations, reporting, specimen considerations, and limitations.
- NIST OSAC Standards Library entry for ANSI/ASB BPR 122-24 Registry context for ANSI/ASB Best Practice Recommendation 122-24.
- Montgomery and Reasor, Retrograde extrapolation of blood alcohol data, 1992 Applied retrograde extrapolation context and the importance of scientifically reasonable assumptions.
- Jones, A.W., Evidence-based survey of ethanol elimination rates, 2010 Forensic context for ethanol elimination-rate variation and retrograde extrapolation review.
