Q: In a “territorial” dispute between two competing businesses, one party got a crime family involved who caused monetary damage to his competitor. What is the halachic perspective?

A: Exposing a fellow Jew’s property to a gentile strongman is a grave sin, known as mesirah (informing). Even if the potential harm is only monetary, there is serious concern that it could easily snowball into physical harm, and even a danger to life. A person who is moser forfeits his share in Olam Haba, is disqualified from giving testimony, and is sometimes considered a rodef, one who threatens someone’s life (C.M. 388:8-11).

A moser who caused his fellow Jew a loss through a strongman, whether gentile or Jewish, is liable for the damage that he caused. Many include this under the category of garmi, while others consider it a penalty imposed by the Sages. Nonetheless, he is liable even on the basis of his own admission (C.M. 388:2, 8; Pischei Choshen, Nezikin 4:8).

A person who was coerced to inform about his fellow’s property, whether under threat of death or physical harm, is exempt. There is a halachic dispute if he was coerced monetarily and informed against his friend to spare himself loss (C. M. 388:2-3; Shach 388:22).