In New York, adultery is still considered grounds for divorce, but no-fault divorce laws have replaced it. Adultery is defined as voluntary sexual intercourse between a spouse and someone other than their spouse. To prove New York Divorce Law Adultery, the plaintiff must provide evidence of voluntary sexual intercourse and intentional and knowing act. Evidence may include witness testimony, photographs or videos, text messages or emails, and private investigator reports. Adultery can have significant implications in a New York divorce case, including grounds for divorce, property division, spousal support, and child custody decisions.