I don't think we are going to hear everything they have in evidence until the judge gavels court in session. Police seem to have confirmed this witnesses' statement somehow, because they seem sure a car was involved and the witness puts one there at the scene of the murder at the precise time of the murder. I imagine they know what type of car too. They just want corroboration to seal the deal. Imho
That makes some sense. I presumed they wanted details to find the perpetrator. If its some sort of rarer style of vehicle that could helped narrow things down