I feel that claiming things were said without recorded evidence would lead to a "he said she said" type situation. Especially when the call was never made from a known number, but rather a "blocked number." How could one be sure someone even made the call instead of the other side fabricating evidence? Would one's sworn testimony to the content be enough? What if the other side lied? It's scary that someone can lie about a fake phone conversation and have it admitted into evidence.
I doubt that this would be allowed, unless there was proof. You should consult with an attorney to discuss your situation.
Likely the judge would not admit the evidence. I would NOT start worrying about every little thing your ex threatens to blurt something out in court.
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Divorce / Separation Lawyer
They could always make the claim, and they may be able to introduce a phone record of a call being placed or received. However, the details of the conversation would be subject to evidentiary rules and if the Judge allowed testimony as to the conversation, the Judge would independently weigh the veracity (truthfulness) of the parties during testimony.
Criminal Defense Attorney
Beware. If the telephone call originated from over a state line, your recording it is probably a felony.
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