In pari delicto not a defense in adultery

Dear PAO,

I have been living separately from my husband for 15 years now. I am currently in a six-month relationship with my boyfriend, and we live under one roof. When my husband came to know about it, he threatened me with a criminal case for adultery, despite the fact that he left me and our daughter and decided to live with his mistress. After all those years of brokenness and suffering, now was the time when I could finally be happy and complete. Can I use as a defense in adultery that my husband was the one who first had a mistress?