Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

If Shelley and Lovelady left and then came back and saw Vickey on the first floor, it doesn't rule out the possibility that she got there before they did. As you know, both Shelley's and Lovelady's testimony about her is VERY ambiguous. It's ambiguous enough for bpete to say that they never claimed to see her at all. 

But, even if you say they did claim it, they certainly didn't claim to see Vickey in the act of descending the stairs. And that again means that she could have come down some time BEFORE Shelley and Lovelady arrived. 

But, if you plant Shelley and Lovelady there right away, it's like they are guarding the place- with eyes open. Then, you have them say that they didn't see Vickey at first, but after several minutes, she showed up, coming down the stairs.

That's the way you do it. You don't need a trek to the tracks.