It depends on the laws in Kansas. In Texas, as long as one party of the conversation is aware of the recording then it’s legal. David knew he was recording so it could be used in Texas as evidence.
I recorded my confronting my ex husband on phone about raping our child (btw he never admitted it in the 45min but also never denied it either) and it was used as evidence in his trial.
If Kansas is one of those states however that BOTH parties must be aware, then it wouldn’t be able to be used although he could still testify as a witness to what was said to him.
That all said, I’m not a lawyer and only know from our experience here in Texas. Maybe
@Charliegizmo49 can help here!