There are a number of reasons to think the Thrill-guy-follows-them-home-and-stalks theory is implausible. One, they left Thrill around 2:15am. So this club-going guy follows them home in his car, waits outside for two hours watching and then decides to go in when (to his good fortune) KR leaves at 4:30am, leaving Faith alone and the door unlocked? No, that just isn't believable. Two, guys who go to clubs to pick up girls may be untrustworthy in any number of ways, but they are not the social type who enters apartments uninvited at 4:30am. That social type doesn't even go to clubs, has an inferiority or rejection complex, etc. The club-going type would just plan on seeing these girls / this girl another night. Alternately, if you have him knocking on the door and being let in by Faith, how did he know her apartment number? He followed them home & waited for two hours? No, not believable. She gave it to him at the club? No, also not believable. She would've given him her phone number, not her apartment number.
For anyone who believes in the Thrill-guy-follows-them-home theory, please present us with a plausible step-by-step account of how this guy gets from seeing Faith & KR at Thrill to murdering Faith with a rum bottle. I would like to see this laid out (step-by-step) in a bit more detail. IMO, it just isn't plausible.