Susan knows David as well as anyone, doesn't she? Laundry--tossing over bannister to laundry area. Either you accept the prosecution spin that he was a neatnik, or you listen to the witnesses.
We know that the Van Dam kids were over, Tuesday, Wednesday, Thursday of that week. They come in the front door, they were in the living room, they went upstairs, they went into the garage, (encouraging jury to listen to the taped interviews with Keene)--the kids are all over. And when the laundry gets tossed down to the floor, there's the transfer.