It depends on what stage the case is at. If your uncle has an attorney, I'd definitely suggest making them aware of the situation. Good luck.
You certainly can do so, however, I would cc the prosecutor to get his respect. Also, as prior counsel has suggested, you may want to first contact your uncle's attorney to let him know what you intend to do. There may be something that attorney would specifically like the letter to address or clarify, in case negotiations are hung up on something. You then could help your uncle even more.
I agree with my colleagues. Contact uncles attorney first before you deal with court or DA.
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