What are the main points in heck tates evidence? what does Atticus know in his cross examination?

The trial begins with the testimony of the sheriff, Heck Tate. The prosecution's attorney, Mr. Gilmer, asks him about the events surrounding Tom Robinson and Mr. Ewell's daughter, Mayella. Mr. Tate states that on November 21, Mr. Ewell came to get him because "some nigger'd raped his girl." He says that he found Mayella on the floor, very beaten up, and that Mayella claimed Tom Robinson had taken advantage of her and beaten her. Atticus questions Tate next, asking whether anyone called a doctor. Mr. Tate says no. Atticus asks where Mayella had been beaten, and Mr. Tate says, with some hesitation, that her right eye and entire right side of her face were bruised, and she had scratches all around her neck. Atticus knows that Tom Robinson could not have raped Mayella because he only has one working arm.

The main point in Tate's evidence was that Mayella was beaten up on the right side (face and neck). This could not have been conduted by Tom as his only working hand is his right hand. However, the cross check proved that Bob Ewell was in fact less handed. This provided Atticus with quite the upper hand in the case logically.