Despite what many employers seem to think, drug testing employees is not free for all they would like it to be. Employers are quite limited in when they can request drug tests for employees.
WHEN YOU HAVE BEEN OFFERED A JOB
An employer may require suspicionless drug testing as a condition when they offer you a job before you start work – if they require drug tests for every new employee coming into the same position. Generally, an employer cannot single a job applicant out for drug testing when others in the same position are not, as it implies the drug test is being done for an unlawful reason, such as because of the applicant's race or disability.
However, once you start working, an employer's right to ask you to take a drug test is very limited. Random testing or routine testing is generally not allowed, except in very limited circumstances like in DOT/truck-driving industries where it is required by law and certain safety-sensitive positions.
An employer is allowed to require an employee to take a drug test based on reasonable and objective suspicion. An example would be an employee who comes in smelling of marijuana, slurring his speech, and with bloodshot eyes. Any reasonable person would suspect that the employee was probably high, and an employer is allowed the same suspicion.
AFTER AN ACCIDENT
Just the fact that an accident occurred is not enough to imply drugs or alcohol were involved and a company is therefore not allowed to require drug tests after a run of the mill accident.
On the other hand, if there are objective, observable clues for believing they were – say the employee was swerving along the road like a drunk driver and reeked of alcohol after the accident, or was caught with drugs on them – the employer may require a drug test based on reasonable suspicion.
EMPLOYEES WITH DISABILITIES
Some employees are required to take medications for disabling conditions that might show up on drug tests. What happens then? Employers absolutely are not allowed to require an employee to submit to a drug test simply because he or she is disabled. If the medication use does not interfere with the performance of the employee's job, the law protects the employee. However, while an employer cannot fire disabled employees for using a legal drug that does not interfere with their job, even disabled employees may be drug tested and even terminated if their medication use creates safety risks to themselves or others.
A SPECIAL NOTE ABOUT MARIJUANA
Despite California's laws permitting medical marijuana use, marijuana use is not protected in the workplace. Even with a prescription, an employee may be fired for marijuana use on the job or coming to work high.