It’s difficult to see how then Oswald could have ever made it out the front door of TSBD just secs before 3 min post shots Officer Barnett supposedly locked the front door.
As already explained, Mr Mason, he didn't:
He left AFTER the building had been locked down.
According to Mr Harry D. Holmes, Mr Oswald in custody recalled being
stopped at the front door by an officer, who only let him pass when he was cleared as an employee by his superintendent of the place. The superintendent of the place was Mr Roy Truly.
From Asst. Chief Charles Batchelor's report on the activities of Deputy Chief of Police George L. Lumpkin:
Mr Oswald knew the precise system that had been put in place several minutes after the shooting-----i.e. Mr Truly at the front door vouching for employees to a police officer-----because Officer Kaminski, having checked with Mr. Truly, allowed him to step outside.
Mr. Billy Lovelady saw this, and told Mr. James Jarman all about it. From Mr. Jarman's HSCA interview:
Well, there was a Billy Lovelady standing out there, he was on the steps, see... Oswald was coming out the door and [Lovelady] said the police had stopped Oswald and sent him back in the building, Billy Lovelady said that Mr. Truly told the policemen that Oswald was alright, that he worked there, so Oswald walked on down the stairs.The Martin film shows that precise system in operation (Mr. Truly is standing behind the glass [right of screen]).
Mr. Lovelady is standing on the steps.
All as per Mr. Jarman's account.
Substitute the black man being ushered through the door here with Mr. Oswald, and we have the scene as described by Mr. Lovelady to Mr. Jarman:
NB! Mr. Oswald was given permission to step outside. He was NOT given permission to leave the scene. But he did.