We have all seen the lost jobs, businesses and broken lives that substance abuse brings.
Many workers use drugs and alcohol after hours with little or no impairment on the job.
But the line is a fine one and always, as with people in general, there are exceptions. From a business and management perspective you must be aware of the presence of substance abuse. You must also have a policy in place to deal with these issues before they occur. Speak with your lawyer first to determine if your current policy is legal. I have seen substance abuse policies that were not legal.