D, his girlfriend, Samantha Sanchez, his friend, Alfredo Sanchez, and three others went to a house party. At the party, two unidentified men confronted D and threatened to kill him and his family because D had killed a young man named Jeremy a few years earlier. D and his companions left the house and the two unknown men, armed with guns, approached them as they walked toward D's vehicle. The men again threatened the lives of D and his family and instructed him and his friends to leave or they would be killed. While they were driving away, the two men fired gunshots at D's vehicle, hitting it at least twice. No one was injured. D claimed that he was scared that the assailants would come by his house and shoot at them again because they had told him they knew where he lived. D armed himself with a 9-millimeter handgun, and he and Alfredo then gathered five of D's firearms-a 12-gauge shotgun, a 16-gauge shotgun, a .22 caliber rifle, a .303 caliber rifle, and a .270 caliber rifle-and loaded them into D's car. D and Alfredo returned to the party. D parked the car near the edge of the property and, saw one of the two men who had threatened him earlier standing outside the house, D approached the man and was hit on the head from behind, fell to the ground, and was kicked. He reached for the 9-millimeter handgun that he had stuffed in his waistband, but it was missing. D got up and ran to his car when he heard gunshots fired from behind him. Alfredo testified that when he saw D running back toward the car, D was unarmed and there was gunfire coming from the house. Alfredo had no idea who had shot first. D grabbed the .303 caliber rifle and fired toward the house where he could see sparks of light that looked like gunfire. D heard more gunfire from a different area of the yard, grabbed the 12-gauge shotgun from his car, and then fired in the direction of those shots. Alfredo fired the 12-gauge shotgun. No one admitted to having fired the .270 caliber rifle, but casings from that gun were found at the scene. Naarah Holgate and Danica Concha were in a bathroom inside the house. Naarah heard what she thought were fireworks and then saw Danica collapse in the bathtub. Danica had been shot in the chest and killed with a bullet that was consistent with being fired from a center-fire, high-velocity rifle. The expert could not say which weapon fired the fatal bullet. Detective Martinez was called as an expert witness to testify about 'gang-related law enforcement and gang culture.' D objected. The evidence was admitted and D was convicted of first-degree murder. D appealed.