He doesn't need to, since everything that happened is on video. He could bolster the story by explaining, but being an 18 year old kid, it is without doubt that he will step on his dick and come off like a fuckhead in a lot of ways. Better to keep him off the stand and let the video speak to the actions of the clearly insane "victims" ... can't step on your dick if you don't testify.
I'd only put a defendant up in this situation if there was testimony I needed from him for an acquittal that I couldn't get otherwise.