So what is it your brother wants to do at this time? He has appeal rights. He can file a Notice to Appeal and then get a public defender or private attorney to assist if he feels the Court acted in appropriately which infringed upon his Constitutional rights.
You say he has filed for a re trial, was that an appeal?
Appeals are not easy and require memorandum of law to be presented as part of his appellate brief.
He may try to get in touch with someone at your local ACLU chapter. They are often over worked but they might find something so compelling about your brother's case they would give him an attorney to assist.
As to the police officer who testified, whom you say had nothing to do with the case - that would be what is called an "expert witness". He is not testifying to the matters of the case, but rather testifying as to the audio tapes and how they function and can be evidence or he was testifying as to the "chain of custody" of those tapes. This is appropriate to have expert witnesses in this regard. It would not be a basis for an appeal
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