The Case of the Deadly Struggle

When neighbors of Hans Meinfurth heard the sound of a gunshot coming form his apartment, they called the police. Soon, detectives Davis and Moreno were at the scene.
The policemen carefully surveyed the situation in the front room. A lamp was overturned. There was some coffee spilled on the floor. A picture hung crooked on the wall. But most importantly of all, the body of Greta Kohler lay face down in the middle of the room.
“It was an accident, I tell you! I couldn’t do anything about it!” Meinfurth insisted. He was sitting in a chair as the policemen kept a close watch on him and recorded his statements.
The photographer took several pictures of the crime scene. He stepped carefully to avoid disturbing any evidence on the floor.
Davis observed the corpse closely. There appeared to be a small bullet wound in the back of Kohler’s head. A lot of blood stained the carpet.
“Suppose we hear your story,” he said as he turned to Meinfurth.
“Greta and I were having an argument,” the man slowly replied. “We had our differences before, but we had always been able to work things out. But tonight was different. She started yelling at me out of control. She wanted me to leave, but I didn’t want to go until I said everything that I was going to say. Suddenly, she pulled a gun out of her purse. She said that she was going to kill me. I didn’t know what to do. I grabbed for the gun in effort to save myself. She was acting crazy, I tell you! Who knows what she might have done if I hadn’t tried to stop her. Anyway, we struggled for the gun for a minute and then it went off. Oh, I can’t believe this happened! If only she’d listened to me, everything might have been alright. Thank God I stopped her before she could have hurt anyone else!” He cried and buried his head in his hands.
“No,” Davis said. “It is you who should have been stopped!”

WHY DID DAVIS SUSPECT HIM?

THE ANSWER
Meinfurth claimed that he and Kohler had struggled over the gun and yet she was shot in the back of the head. It would have been impossible for this to happen if he really acted in self-defense. Later, he confessed to the murder.