Actually it doesn't. One court decision does not offer blanket coverage. Each case is different and in this one, Zimmerman will ultimately be found not guilty despite the crap you keep posting.......
wtc911 has been told by several posters that the cases he's citing aren't applicable at all, to non-hearsay testimony. And Zimmerman's testimony and statements aren't hearsay. He was there. Eyewitnesses or not, he may testify. There is no need for independent eyewitness corroboration - although independent eyewitness evidence is VERY VERY helpful in this case.
Of course, one is always free to challenge the credibility of testimony, even non-hearsay testimony.