Shortly before Graves moved along the side of the ambulance and toward the
back door, Bieberdorf did the same. It appears that Bieb got into the
backseat first. The problem is that there wasn't enough room for two
people in that backseat (there was only one seat), so it had to be one or
the other sitting there.
Wolfe and Hardin sat up front. Dhority and Leavelle got into the rear, and
sat or crouched down beside the gurney. That leaves one available seat for
Bieb or Graves (passenger second row since the other seat was folded down
to fit the gurney).
Dhority said only that he was in the ambulance when Oswald was transported
to Parkland. He gave no specifics about who else rode inside the
ambulance.
Leavelle's report states that he rode in the ambulance with Graves,
Dhority, and Bieb.
Graves said he rode in the ambulance with Leavelle, Burgess, and Bieb.
Bieb was the most specific but he changed his story (which still ended up
being incorrect). In his witness report it states that he rode in the
rear of the ambulance with Leavelle, and that two other detectives went
along (he couldn't name them but said they sat in the second row).
However in his WC testimony Bieb said that the report was incorrect. He
said that he actually rode in the second row of the ambulance and Leavelle
sat beside him, while two other detectives were in the rear. But there
was only one seat in the second row so Leavelle couldn't have set next to
him there, and we can see Leavelle get in and out of the rear anyway.