Just because your employer has given a false reason for your termination does not necessarily mean that you have a case for wrongful termination. The key is whether or not the reason given by the employer is merely an excuse, or pretext, for an illegally motivated termination.
In California, like most other states, employment is at-will, meaning an employer can terminate an employee at any time as long as it is not done for illegal reasons. Typically examples of illegal motivation include discrimination based on disability, gender or race, or retaliation for engaging in a protected activity. A pretext would be a stated reason for termination by an employer designed to hide the employer's true motivation. It is even possible that the pretextual reason has some elements of truth. This might come up in a situation where an employer was not entirely satisfied with the employee's work, states this as the reason for termination, but in reality would not have terminated the employee if not for the illegal motivation.
The process of determining whether the reason given by an employer for a termination is a pretext will often require the initiation of legal proceedings. By gathering documents, taking depositions, and obtaining witness statements an experienced employment law attorney is able to uncover the truth. In some cases, the reason given by an employer might not be true but the employer still has not wrongfully terminated the employee. However, other times, after a thorough legal investigation, it can be proven that the employer provided a false reason for termination and/or that the reason given by an employer was a pretext designed to cover-up an illegal action.
If you think your employer provided a false reason for your termination and that this was done to hide the fact that the employer's actions were illegal you should consult with an attorney immediately. An experienced employment law firm will be able to evaluate your claim and recommend if further action should be taken.