AI
No, the defence (or anyone else involved in a trial) cannot invent a conversation. All evidence presented in court must be factual and truthful. Inventing a conversation would be considered fabricating evidence, which is a serious criminal offense, potentially leading to charges such as perjury or perverting the course of justice.
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The only window where Nevill called Jeremy (aledged evidence) is after his 4 bed shots (evidence) & before the kitchen attack (evidence).