This story starts with a stay-at-home-mom from the Denver suburbs.
Her name is Abby McLean. She's 30 and lives in Northglenn, Colo. She was driving home from a late dinner with a friend two years ago when she came upon a DUI roadside checkpoint.
"I hadn't drank or smoked anything, so I was like, 'Let's go through the checkpoint,' " she recalls.
McLean is a regular marijuana user but she insists she never drives while high.