11 TV Hill: Troopers training to detect drivers impaired by marijuana

And, what goes into training that Maryland state troopers receive to identify drivers impaired not by alcohol, but by cannabis? Drivers who have a blood-alcohol level of point 0.8 are considered impaired. But what -- and how -- does one detect someone under the influence of marijuana? The odor of marijuana is not enough for police to make an arrest. So, last month, Baltimore County police officers took part in a training aimed at getting some answers to the question.