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<p>There are differences between factual evidence, opinion, and argument.</p>
<p>Most witnesses can testify only to facts that they observed, or to lay a foundation to bringing in physical or documentary evidence. If there are other facts that contradict whatever they say, it will generally need to be brought forth through the testimony of a different witness. In some cases a contradiction can be brought out in cross-examination, but that only works when you are directly challenging the witness. That is, if GZ were testifying and said TM jumped out of the bushes at point X, a lawyer on cross-examination could bring out the fact that there were no bushes at point X. </p>
<p>But if you are asking the police officer who took the statement – she is only testifying to the fact that the statement was made. If she took the statement at the police station, then she is not in a position to testify as to whether there were any bushes or not. On the other hand, if the question were posed to an officer who was also present when GZ was taken on the walk through, the question could be posed to the officer: “did you see any bushes” there.</p>
<p>I’d add that GZ’s statements are admissible under an exception to the hearsay rule, as an “admission” – that is, the reason that the prosecution can introduce the statements is NOT that they give GZ’s side of the story, but only because they contain admissions of wrongdoing on his part. </p>
<p>As to opinion: only a duly qualified expert can give an opinion on most things (except the sort of things that would be within anyone’s ability, such as estimating distance). At the same time, expert opinion can’t be used to supplant the stuff that is expected to fall within common knowledge. So an “expert” for the prosecution might be helpful to point out some problems with GZ’s account – such as whether or not it would have been possible or likely for TM to sit up and make a statement after being shot. But whether or not there were bushes is not a something for expert testimony – but that could be brought out through direct factual testimony, perhaps by a police officer who took measurements and photographs of the crime scene. </p>
<p>So some of the contradictions will be brought out through other witnesses, testimony, and exhibits – but it may be protracted and not immediately obvious how all the dots are connected. A good attorney will try to make the relevance of testimony clear during the course of testimony, but in some cases it may not be clear until the point where the prosecutor gives his closing argument. (And a good prosecutor will also hold back on some points that aren’t so obvious, so as not to tip off the defense as to the entire argument). </p>
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<p>The prosecution would not have introduced GZ’s statements unless they were pretty certain that they could counter them – they aren’t required to let the jury hear GZ’s side of the story in their case in chief. It only helps their case if it supports a narrative that GZ shot TM, and then lied to the police about what happened.</p>