An individual harasser at workplace in California, whether he / she is a co-workers or a supervisor, may be personally liable for sexual harassment under the Fair Employment and Housing Act (FEHA). This means that the employee who is a victim of sexual (or other) harassment, may be able to pursue legal action against both his or her employer and the individual who causes harassment and creates hostile work environment.
FEHA defines “supervisor” as an individual who has either (1) the authority to hire, transfer, suspend, lay off, recall, promote, discharge, assign, reward or discipline other employees; or (2) the responsibility to direct other employees, adjust their grievances, or effectively recommend such action on grievances, provided that the exercise of the authority or responsibility requires the use of independent judgment. Cal. Government Code section 12926(r).
For more information about FEHA please visit the site of California Department of Fair Employment and Housing.