IMO this is a woman.
The angle of her arms do not suggest she's doing a backbend; that requires support and control. The arms look too straight and hanging too far in front of the head to be a controlled backbend.
It is therefore likely that we are looking at Alcala's legs.
He is either facing her and holding her by her waist and legs as her upper body is hanging down, or he is facing away from her and she is being effectively dragged. It is difficult to determine which is likelier.
I also believe that the woman in this photo is also in another photo that was taken shortly beforehand.
There is a woman seen close to a tree and foliage doing what appears to be a naked pose whereby she is holding her right leg up and straight at an angle to her frame that is facing in the opposite direction. A pose that would be familiar with a gymnast, a dancer, a martial artist, or someone with a degree of flexibility who could use an open rotation of their hips to extend their leg up, back, and then adjacent to their upper frame.
I believe that the "backbend" photo is the same woman who is earlier performing the leg extension.
Judging by her countenance, her eyes, and the redness on her throat and upper chest, it appears that the "backbend" woman is in significant distress. She may have even been choked out and then brought back by Alcala just before the "backbend" shot is taken.
If that's indeed the case, then it would seem that this woman was a murder victim.
What are everyone's thoughts with regards to the "backbend" photo being the same woman who is seen with a raised extended leg? (a photo that has both a full version and a close up version of just her face)