In New York, you have the obligation to retreat and not use deadly physical force if you can do so completely and safely.  However, there are exceptions to this rule including you do not need to retreat if you are in your own home and you were not the initial aggressor, are a police officer acting within the scope of your duties, or you believe that someone is committing or attempting to the crimes of kidnapping, forcible rape, forcible criminal sex act, robbery, burglary, or arson.