The Frederick Police Department offered some local residents a detailed lesson this week in traffic enforcement, criminal investigations and driving while intoxicated.

About 20 people met at the Charles V. Main Training Facility on Plant Road for the fourth of 10 classes in the 15th Citizen Police Academy.

Cpl. Sam Bowman, who has been with the force for about 20 years, demonstrated the difference between laser and radar guns in order to detect how fast a car is traveling.

The laser can measure a car's speed from about 1/2 mile to 3/4 mile away, he said, and is more accurate.

Radar guns pick up almost anything moving and measure the speed of the largest object coming toward them.

Bill Douwes, crime analyst, explained geographical profiling and prediction analysis, looking for crime patterns and interpreting the data that lead to arrests.

Sgt. Clark Pennington talked about how alcohol and drugs affect the body and how police look for clues indicating a driver is impaired.

Next week, the class will observe drunk people and test their levels of intoxication.