What the Defense is looking for is ANY WHITE CAR (hopefully an Elantra) that can be seen ANYWHERE in ANY OF VIDEOS, NOT NEAR THE HOUSE, when the murders occurred. Maybe even going the opposite direction so that there are TWO white cars.. .trying to create reasonable doubt.
If they find that, then that is their alibi. that it is BK.
That, to me, is why they TRIED to use the "We have an alibi but do not know who will come forward to give it" statement.
Video of white cars in the night, that night, is what they are looking for. It is a very common car and there will probably be a white car somewhere else in Moscow, Pullman or whenever, between 3:30AM and 4:30AM that they will claim is BK's car.