Prosectuion can certainly ask to have it suppressed, but it is up to a judge. You attorney should be able to play the tape as part of his request to suppress the whole stop and have the matter tossed out of court. Sounds like a bad cop, who just took it out on your brother.
The tape constitutes exculpatory evidence (evidence that goes towards your brother’s innocence). It is absolutely discoverable and cannot imagine a judge suppressing such evidence (reversible error). Normally judges sign entries submitted by defendants ordering that such evidence be preserved. Suppression motions are filed to suppress evidence tainted by law enforcement’s violation of your brother’s constitutional rights (unreasonable search and seizure actions), not protect the State’s ability to prevail at trial.
This answer is offered for informational purposes only. It is not offered as, and does not constitute, legal advice. The answer presumes you are not currently represented by an attorney who knows your specific circumstances.