If someone opens a legal case against someone,in the secular court, and doesn't go through the local Beis Din, and the best form of defence is to open a fraud case against that person, who by the way is a Jew, is it permitted to report the person to the secular authorities or not? The proofs are straight forward and are all backed up by documentation. Failure to report the fraud may result in quite a big loss
Answer:
Being that your intent is to protect yourself from the secular court which you were taken to in contradiction with halacha, you may use this as a means to protect yourself from losing money in court.