Hi

I am a manager at a restaurant and I suspect one of our kitchen staff of being on drugs. He shows all the signs, red eyes, lack of concentration and a general demeanor that fits with drug use. This employee was not always like this, the change has come about in the last few months. We do not have a written contract with this employee so I am unsure if I can just test him. And if I do, do I just fire him on the spot?

How would I go about a test?

Thanks in advance for any answers