Let's have a closer examination of something that really puts Bill Shelley in the spotlight as Oswald's accomplice.
Oswald may have been a lot of things but he was not stupid. Beyond the mumbling loner known to his work colleagues, Oswald was an intelligent and articulate man. His various radio and television appearances demonstrate this with clarity as does the fact he taught himself to speak Russian.
When a person gives an alibi to the police they know they have gone on the record and that this is the version of events that will be used against them in a court of law. For anyone accused of a crime, the most important element of their defense is the 'alibi'. They also know that once the alibi is given it will be checked to see how 'cast iron' it is. For crimes such as shooting police officers or Presidents, this is doubly so.
An alibi that turns out to false is a massive red flag to investigating authorities.
If a guilty person is going to give a false alibi it must be one that is incredibly difficult to verify or one that has been agreed with an accomplice.
Looking through the various notes and reports pertaining to Oswald's interrogation, his alibi has a few different elements:
According to what Oswald reportedly said -
1] He was in the lunch room on the first floor (the Domino Room) when JFK's limo drove by the building.
2] After this he went up to the second floor lunchroom to buy a Coke
3] He bought the Coke and was drinking it when Baker burst in, gun drawn.
4] He went back down to the first floor.
5] At some point he got together with Bill Shelley.
6] As a consequence of his conversation with Shelley, Oswald decided to leave.
7] Oswald left the building.
The most significant element (imo) of Oswald's alibi is his interaction with Bill Shelley. Apparently, Oswald credits Shelley with his motive for leaving the building. The importance of this cannot be stressed enough because it is Oswald's decision to 'flee the scene' that puts him well and truly in the spotlight as a prime suspect on the day of the assassination. Even if he actually pulled the trigger, he has no reason to run immediately. He has already encountered the police, seconds after the shooting, four floors below the location of the shooting and has been given a pass. They can't immediately trace the rifle to him, they can't use fingerprint evidence against him on the day. All he has to do is hold his nerve, say he was on the second floor lunchroom all along and skip town later that day. Instead, he leaves the TSBD building and appears to be making a run for the border when he crosses paths with J D Tippit.
So let's imagine that Oswald is the shooter and is trying to come up with a false alibi. One that will stick in a court of law or at least convince the DPD.
He's being asked - why did you flee the scene of the crime? Obviously, he has to come up with something convincing but something that would be almost impossible to verify.
Instead, he basically says that Bill Shelley said it was OK for him to leave!
Why on earth would he mention Bill Shelley? Why would he say it was Bill Shelley who recommended he leave for the day?
After his arrest, Oswald saw Shelley as he was being taken into the interview room because Shelley, who was having his affidavit taken, had to vacate the same room. So Oswald knew that all they had to do was ask Shelley if such a conversation took place. It's the easiest thing in the world to check and it can be checked almost immediately.
According to his testimony, Shelley (like nearly everyone else) hardly knew Oswald at all except as someone who worked at the TSBD building. Why would Oswald, an intelligent man, think Shelley would back him up? Why would he take such a ridiculous risk? Why would it even cross his mind to offer such an easily checked alibi if he knew the detectives could immediately ask Shelley if it was true?
The answer to this question is obvious - Oswald did it because he fully expected that Shelley would back him up!
Which of these two options makes sense - that Oswald was so utterly stupid as to include Shelley in a false alibi that could be checked out immediately, leaving him looking completely guilty...
...or that Oswald fully expected to be backed up by Shelley, which is why he felt comfortable telling his interrogators about it?
Of course, when asked, Shelley denied all knowledge of this interaction with Oswald. This is from an FBI report about Shelley the day after the assassination:
"OSWALD said nothing to him about leaving work early or going home, and he did not give OSWALD permission to leave work.
He is still being asked about it in his WC testimony:
Mr. Ball: Did you at anytime after the President was shot see Oswald in the building?
Mr. Shelley: No, sir.
Mr. Ball: Did you at anytime after the President was shot tell Oswald to go home?
Mr. Shelley: No, sir.
Fritz makes the point that Oswald was cool and collected during the questioning, as if he'd experienced this kind of thing before, so the idea that a panicked and desperate Oswald blurted out the first name he could think of as an alibi is a non-starter.
It must rate as one of the weakest alibis in law enforcement history and something only an utter moron would come up with.
Or...
...Shelley was lying...
...again.
He lied about his movements in the immediate aftermath of the assassination and he was lying again about interacting with Oswald.
Of course Nutters will cry "but Oswald was crazy".
That may well be, but he wasn't so stupid as to think his Shelley alibi would stand up if it was false.
Oswald expected Shelley to back him up.
But only an accomplice would do that.