Hello, can you help me with this homework

Based on the scenario below do you believe a crime has occurred? Why or why not? If Joe was arrested, what is a possible defense? Explain your position.

Susie Jones was the longtime girlfriend of Joe Smith. From the outside, they had a very normal relationship, although there were quiet rumors that Susie had a tendency to become a bit violent when she was drinking.One night there was much screaming and yelling heard from their apartment and a neighbor called the police to report what sounded like possible domestic violence. When the officers arrived on scene, they knocked on the door and were greeted by Joe standing there with cuts and scratches on his face and arms as well as an abundance of blood on his shirt. Suspicious of what was occurring, the officers entered the apartment and found Susie lying on the ground with a knife protruding out of her abdomen.Joe proceeded to tell them that Susie had been drinking and an argument broke out. She came at him with a knife and Joe tried to take it away from her to protect both him and her. During the tussle, the knife somehow was turned around and stabbed her.