Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

Here is something else to consider about Dorothy Kilgallen: 

We can be absolutely certain that Ruby told her the following: that he had no plan to shoot Oswald; no intention of shooting Oswald; that no one put him up to shooting Oswald, and that he didn't realize that that he shot Oswald until Dallas Police told him on the 5th floor that he had done that. 

As for the idea that he was involved in killing Kennedy, we can be absolutely sure he expressed his pain and grief over Kennedy's death. I doubt that he volunteered that he didn't kill Kennedy, and if she asked him whether he was involved, I'm sure he responded with aghast and revulsion, as in, "Are you nuts?" 

We can be absolutely sure of all that because there is no reason to think that he told her anything different than he said in other contexts.  

So, the question is: did Dorothy Kilgallen believe him, or did she think that he was lying? Well, let's remember that she was the world's leading expert on detecting lying. On What's My Line, there would be three contestants, and two of them would be lying- claiming that they were the third contestant.  Her job was to determine which two were lying, and which one was telling the truth. And Dorothy was the best- the smartest and most cunning of the questioners.

And Jack Ruby was not the least bit cunning. He didn't have a Machiavellian bone in his body. And why would he talk to her at all, let alone twice, if he intended to lie to her? Why would he insist on having a polygraph test if he intended to lie? He wouldn't. 

We can be sure that Jack Ruby told her the truth, and we can be sure that Dorothy Kilgallen got a read on him and she assessed that he was telling her the truth. And the people who killed her surmised all that, and that is why they killed her. 

Don't listen to the people who tell you that Jack Ruby was involved in killing Kennedy. He loved the man. He wasn't putting on airs. He wasn't an actor. Their alternate story of the assassination does nothing but serve the interests of those who actually did kill Kennedy and Oswald.