Filing federal & state tax returns without spousal consent or knowledge?

My inlaws have been separated, but not divorcerd for 20 years. My mother-in-law lives in Europe (for 19 years) and has never recieved spousal support. I recently discovered that my father-in-law has been filing both Federal and State tax returns "married filing jointly". I contacted my mother-in-law and she had no idea of this. Recently, he has been E-filing. Since she is unaware of this, I can only ume that he has forged (physically and electronicaly) her signature. This alarms me. I am certain this constitutes both filing a false return and forgery issues. What should I do to protect her? Am I making too much of this or is it fraudulent?? Thank You!