That is untrue, a defendant in a criminal case can take the 5th amendment so as to not incriminate themselves, any witnesses they have can still testify as long as their testimony is otherwise admissible.
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Of course they can. As pointed out by the previous lawyer answering this question, all testimony must be admissible (i.e., relevant, non-hearsay, based on personal knowledge or qualified expert opinion, etc.) but no party to civil or criminal litigation needs to testify as a pre-condition to calling other witnesses. That said, and depending on circumstances not apparent from your question, the defendant may be best served by taking the stand. See a local lawyer who can provide you personal representation (if you're a party to this litigation).
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