Protected Class Discrimination
Many people when they are discharged claim they have been discriminated against but almost never have a solid case for proof in the eyes of most agencies and attorneys.
The main one I will be covering is retaliation. This would usually take place for attempting to report a behavior or incident that has taken place against someone. If you previously experienced some sort of action or behavior towards you that was unwanted and reported it to a supervisor, human resources, manager, etc then you have just engaged in a protected class activity. What this means is that if anything takes place after this event, such as retaliation then you would have a solid legitimate case for discrimination due to retaliation.
Usually this retaliation would take place shortly after you have made your report regarding an unwelcome action. This is the time when writing down each and every negative action that is said or done to you will be important. Typically, after reporting the person suddenly received multiple warnings for minor issues or for an issue others have done without being warned. Then the employee would be discharged on an unrelated matter and the employer would consider the employee discharged due to insubordination, failure to follow the employer’s policies, etc.
At this point you could seek legal advice regarding retaliation, and contact your state and federal agencies so you have recourse against an employer who decided to retaliate against you.