It's worth noting that (if I haven't mixed up anything):
- claim that Cotton drove Thomas to and back from work comes ONLY from Thomas,
Next door neighbour of the Arnold's was asked about the 23'rd on the 24'th - and then, less than 24 hours after it happened she was confident in seeing Fran multiple times during the day and afternoon, seeing their car not leaving their driveway, and being offered help with setting up the party by Fran.
- claim that Debra drove Thomas to the bowling alley also comes only from Thomas
No mixed up details about her picking him up from there. She did. And she used her car to do so.
There is no friend, buddy, coworker, client no one I could find even mentioned anywhere, in any article, any VI's post that there was someone like that who came forward to publicly state that yeah, he WAS with Thomas on that day, spend some time with him on that day, met him somewhere, worked with him, chatted briefly while picking up/leaving a car at his business. Nothing like that.
There was a claim that Debra was the one to drove him TO the bowling alley, but it doesn't look like it came from Debra.
There was also a claim from Fran - that she was with him at the workshop, but highely unlikely that she did.
She could be covering up for him... that's a possibility. But what we know as a fact, that came from multiple VI and both surviving Arnold's children is that Cotton was abusive and violent. They didn't have happy home life. Seems like both girls did what they could to leave that house as soon as they could.
No idea if Cotton was abusive only towards his daughters, or if Fran was also mistreated, but this is a thing that I considered before, while spamming this thread with my ideas. And that is that women in abusive relationships tend to not behave in a way that would be considered "logical" or "reasonable" by someone who isn't.
I can see her unwillingly giving Thomas alibi and that's not even unlikely scenario.
One way or another, doesn't matter that much cause he didn't take this "alibi" and she backed out of it later too.
He was first called at the bowling alley at 8pm. It's not certain if bowling alley was called before but he wasn't there or couldn't be located. One way or another, that's 8pm.
So in the scenario that he's responsible, he could have even as much as EIGHT hours to meet/locate the girls, commit triple murder, hide their bodies, clean up, dispose of them, come back and show up at the bowling alley like nothing happened.
May be much less, no way of telling how reliable are those Brasilian bloggers who claimed to speak with him - cause there he allegedly talked about heading home to take a shower before getting a lift to the bowling alley from Debra. That could be completely fake.
Eight hours, maybe even over 8 hours of time gap between last sight of the girls and his first confirmed location.
That could give him good, reasonable 2 hours to drive somewhere, drop the bodies, sunk the car, hide or dispose of the barrels.
Two landfills in 10-15 mins drive from the workshop. All five in under and hour long drive from the workshop.