SANFORD, Fla. -

Defense attorney Don West told a “knock, knock” joke during opening statements in the George Zimmerman trial Monday.

“Knock, knock. Who is there?"

The punch line: "George Zimmerman. George Zimmerman who? Ah, good. You're on the jury!"

No one in the courtroom laughed at his joke. Jurors laughed at his failed attempt. Then he tried to tell a personal story, but Judge Debra Nelson interrupted. She asked him not to personalize his statements, and to stick to the evidence. And so he did.

"There are no monsters here," he said.

The prosecution’s opening statement was emotional and a short 20 minutes; the defense took about two hours to present diagrams, photos and to play the audio of police recorded phone calls twice.

West insisted Zimmerman was not unemotional about the Feb. 26, 2012. He said one of Zimmerman’s co-workers at Digital Risk saw him cry and the fatal shooting was one of the most traumatic nights of his life.

On Zimmerman’s injuries, West said there was evidence that showed Zimmerman’s head impacted a hard surface of concrete. He said the paramedic suggested that Zimmerman go to the hospital to be checked for possible head trauma.

West also added the doctor's office where he got the check-up didn't have an X-ray machine to determine if Zimmerman had a broken nose.

West said Travyon Martin appeared threatening, because it was a dark and rainy night and the teen was “over six-feet tall and wasn't skinny” and nobody in the neighborhood was able to identify the teen. They were, however, able to identify Zimmerman.

West peppered his statement with facts: Zimmerman was placed in the back of a patrol car and handcuffed after the shooting. He was carrying his Kel-Tech handgun “the right way.