It depends on the circumstances. Self-defense in domestic abuse cases is a difficult claim to prove. By no means was Joann right in lying under oath. But she was afraid for her life. What they charged her with is lying to a grand jury which has a stiffer penalty than perjury.
Prosecutors have discretion in cases.
They should have understood her tremendous fear of the man and the dynamics of domestic violence. I think they should have not prosecuted. Let's be real. A grand jury determines whether there is enough evidence to prosecute. The jury determines the outcome of the trial.