Rhett, your theory about it being a female killer never came to my mind-only because of the two unidentified males seen leaving the stacks-just because the murderer had to use alot of force doesn't mean it couldn't have been a female. (Look at the Manson family's female members)
Jealousy is the old green eyed monster. Betsy looks absolutely beautiful in the photo I've seen. She was an outstanding student. Was about to marry the man she loved. From accounts in the articles that littlehorn provided, she was outgoing, caring, and wanted to try to change things for the better (Peace Corp etc.) Many things to be envious about. I dunno, Rhett, you at least gave me something to think about.
littlehorn, in post #50, you were saying that maybe Betsy came upon 'something illicit' in the stacks. That is what I was referring to about it being a part of the library that had little use. The 'drug deal' was just an example. It could have been almost anything.
As far as the 'once' thrill killer theory...just because he wasn't caught for Betsy's murder doesn't mean he never killed before or again. Look at all the unsolved murders still today. It also doesn't mean he wouldn't pick a place such as a library to kill somebody. Thinking like a sane person doesn't work in all murder cases. Some perps sneak into homes and kill or kidnap their victims while other family members are there (not every instance is it nighttime). That is one of the ways they get part of their 'thrill'
Just like the rest of you, I'm banging my head against the table, too. Everything I think of just leads me back to " Geez! It couldn't have happened that way...or because of that..but maybe...?"
I just hope somebody comes up with the right question or answer to help solve this.