The short answer is that you can be fired. This is based on the premise that the nature of an employment relationship is one of trust which requires an employee to show utmost good faith towards the employer. Accordingly, our labour laws recognise that an act which is inconsistent with this element of trust may warrant disciplinary action, and where serious cases of misconduct are involved, could even warrant dismissal.
Employees, in addition to performing their duties diligently, are therefore required to protect the business interests of their employers, which can extend to adopting an active approach in helping employers to detect perpetrators of misconduct against the business.
Accordingly, in circumstances as you have described and where one or more employees are aware of wrongdoings by other employees and which have not been reported to management, the principle of “derivative misconduct” comes into play. This principle recognises that the innocent employees who are silent about wrongdoings of their guilty colleagues may make themselves guilty of a derivative violation of trust and confidence if the employer can show that the employee probably “knew or must have known” about the actual misconduct.
Our Labour Court recently also recognised that an inference/conclusion that an employee knew or must have known about a wrongdoing can be drawn from evidence that the employee was there during the time when the wrongful act was committed. There may also be circumstances where an employee is obliged to exonerate himself by informing the employer that he was not present when the misconduct occurred, particularly where the employee is reasonably expected to be aware of the wrongdoing. Examples hereof include striking employees who were present or participated in a strike that resulted in violence and where the evidence shows a high probability that they were aware of the violence or of the perpetrators of the violence. Our courts have recognised that there is a duty on such employees to exonerate themselves by reporting the information available to the employer when presented with the opportunity to do so.
Of course circumstances differ from case to case and it would be advisable that you seek the help of a labour specialist to assist you with an assessment of the merits of your employer in dismissing you for the actions of your colleagues.