Just because the Prosecution has evidence, it doesn’t mean their interpretation of it is representative of reality.  It is the job of the defense attorney to find fault with the prosecution’s interpretation of that evidence.  To do that the needs a working understanding of the law and how it works.  \n\nAll of the work of the prosecution and the defense attorney is judged by the jury as to its validity.  \n\nTogether their goal is to produce justice as allowable within the context of the law and the common sense of the jury.