Proving impairment from drugs can be difficult because different substances have different effects, and individuals do not respond identically to the same concentration.
Alcohol has familiar concentration thresholds discussed in DUI law. The video explains that South Carolina does not apply an equivalent single impairment threshold across other drug classes. A laboratory result therefore needs to be considered in context.
A DUI drugs defense should examine the recordings and the driver’s behavior. The question is whether the evidence establishes that drugs materially and appreciably impaired the person’s ability to drive, rather than merely showing that a substance was present.