Materially and appreciably impaired
On one hand, a defendant does not have to be drunk in order to have his faculties materially and appreciably impaired.
On the other hand, having consumed alcohol or drugs does not automatically mean that the defendant’s faculties are materially and appreciably impaired.
“The trial judge properly charged the jury in part on the standard of proof necessary to establish driving under the influence. However, he improperly instructed the jury to use the standard of one's driving ‘who had not drunk any intoxicating beverage.’ Prior case law speaks in terms of the ability to operate a vehicle with reasonable care and as a prudent driver with due regard for himself and others. These are proper standards with which to compare the defendant when determining whether defendant's driving abilities were materially and appreciably impaired. The trial judge also instructed the jury to consider the standard of a driver who had not partaken of any intoxicating beverage. One violates the statute by operating a motor vehicle where he has partaken an intoxicating beverage to the extent that he cannot drive a motor vehicle with reasonable care, or cannot drive as a prudent driver would operate a vehicle.” State v. Kerr, 330 S.C. 132, 144 (Ct. App. 1998)