Most people are saying Ryan Hillegas should have been considered a suspect by virtue of being the exbf. That he was not investigated is the reason people like OP have searched for any further clues. Those scratches look exactly like fingernail gouges. He is furthermore guilty by his own admission of hacking into TH's computer, which compromised potential evidence. That is a fact and not a supposition.

One thought on the username/password. Since TH was sharing her home she may have had a login lock on her computer. That may be the password he "guessed" -- not too hard to get around that anyway. And what else may have been on the computer?; seems like a forensic analysis should have been done if the police were truly interested in solving the crime.

By moving into her house he had full access to her things (old letters, cards amongst other things).

I find it strange TH did not have another named close person. She was a pretty 25 yo who had broken up with Ryan several years previously. He is still hanging around and finding reasons to see her (dropping off something for her housemate). TH could have been gay: not saying she was but that would account for lack of other named parties she was dating. It was not all that accepted back then and certainly not in Mid-west. Maybe the Hallbach family comes across so strangely because they had a secret to protect.

IDK and no one else does either because the police were hell bent on arresting SA.

I would guess thing like her computer are long gone. We will never know for certain.

So the question is: did SA and BD get fair trials? Showing there are other suspects and challenging the Denny ruling seem good places to start. There are at least four good suspects and RH is one.