A controversial, yet sometimes useful tactic used by parties of a divorce case is to record a phone conversation between the spouses, usually one spouse doing so in secret from the other. The idea is that the unknowing spouse will slip up and say something so profound that, if brought before a judge, it could very well impact their decision on things like child custody and child support.
A common question of whether this recording of the phone call, and using it as the “smoking gun” in your case is answered by N.Y. Penal Law §§ 250.00, 250.05. This law is what is known as a “one-party consent” law. New York makes it a crime to record or eavesdrop on an in-person or telephone conversation, unless one party to the conversation (either spouse) consents. And here, the consent is the act of the spouse that initiates the recording of the conversation. In short, if you are going through a divorce and you record a conversation between you and your spouse, and they are not aware of it, you are, by law, allowed to do so. Furthermore, these conversations are admissible in court, and the content of these conversations vary from state to state.
Other states have a “two-party consent” law, which means that both spouses would need to consent to the conversation being recorded, which makes it a lot less likely to get something out of them that can hurt them in court.