Attorneys for officer Devin Brosnan refuted Fulton County District Attorney Paul L. Howard Jr.’s assertion that Brosnan would be a “state’s witness” in the case against Garrett Rolfe.
If I were Brosnan, I would not want to have publicly declared I would be the state's witness. I suspect this is damage control - note that the lawyers did not claim Howard lied. They promised his cooperation with the office just as he cooperated with the GBI.
I suspect that Howard did not lie and the lawyers are lying at this point, but that could be wrong - Howard could have jumped the gun.