First, when you instructed the employee/driver to test and they admitted to using a controlled substance. At that time, it is considered the same as a “refusal to test or positive”. An employee/driver can voluntarily admit to using alcohol or controlled substance and not be subjected to the DOT return-to-duty requirements providing the driver does not self-identify in order to avoid testing. There are other restrictions that apply in order to exercise this exclusion; refer to §382.121.
Secondly, the employee should not have been instructed to “test anyway”. Again once the employee self-identified to using a controlled substance after they had been notified to test, it was basically a “done deal”, in order to return to a safety sensitive position they are required to go through the return-to-duty process. Lastly, there is specific cutoff concentrations associated with each one of the drugs or drug classes that the lab is testing for. If the specimen is not at the cutoff levels or above, even though there are traces of a drug metabolite the result will report as a negative. It is extremely important to note that anytime a person is suspected of being under the influence, they should not be permitted to drive.
They should be escorted either to the collection site or home depending on the circumstances. Due to legal liability and safety issues, should the unsupervised individual be involved in an incident or accident after you had knowledge or speculation of them being under the influence, there could be serious legal consequences to the employer, supervisor or company as well as serious safety consequences to the collection personnel, general public or employee/driver.