Here’s the cite for the DWI holding in NC. http://nccriminallaw.sog.unc.edu/light-just-turned-yellow-retrograde-extrapolation/
FORENSICS and LAW in FOCUS @ CSIDDS | News and Trends

Its all about scientific support, or lack there of in the appellate halls of North Carolina.
DWI ‘extapolations’ of BA to assume alcohol ‘eliminating’ phase at time of testing take a hit.
Thanks to GGWolk