We have a small construction company with a crew of 5. The owner hires guys now and then from our towns correctional services pre-release to help them get back on track with a healthy life style. Recently we have become suspicious of one of our other employees. We think he may be using drugs, but denies it when confronted. I want to set up drug testing for our employees but am curious if the law has any regulations on the way we have to it. The guys from the pre-release get tested a few times a week, and one employee is in the Army reserves and gets tested throughout the year. We also have three part time employees who work in the office keeping our books. My question is, if we drug test our employees do we have to drug test the ones who are already being tested though other organizations? and do we also have to drug test part time employees?