When Michael confronts Carlo, I think he already has decided that Carlo was defintely responsible for Sonny and is to answer for it. If I am correct in that belief, why does Michael care so much about who approached Carlo. He has already killed both, so to me it seems a moot point as to which one approached Carlo. Any thoughts?

Yes C. one of those moot points that makes for a good movie. At that point Michael did know from the Tessio-Barzini meeting and other indicators, and he was going to kill Carlo whether it was Tattaglia or Barzini or Cuneo or Stracci, but then we wouldn't have had that whole dramatic build up to Carlo putting his foot through the windshield.

Why shouldn't he care who approached Carlo just because ALL the Family Heads were now dead?

A man in Michael's position would want to know every detail possible of what's going on with his enemies, who's behind what, etc. It would have been a careless mistake to do away with Carlo without extracting that information from him.

That aside...Michael may have already known it was Barzini who approached Carlo. But the finality, the satisfaction of having this betrayal confirmed by Carlo, and then watching Carlo die himself may have been another thing Michael was after.

Apple

There's a passage in the book--which I don't have in front of me at the moment--that talks about how even at that late date, Mike was still a tiny bit unsure about the extent of Carlo's involvement, and still needed that final bit of confirmation.

If no one else does this afternoon, I'll post the quote later.

Plaw hit it. Mike needed proof beyond a reasonable doubt before he killed his brother-in-law. Here's how Puzo wrote it:

Michael was still not that confident of his right, still feared being unjust, still worried that fraction of an uncertainty that only a confession by Carlo Rizzi could erase.

I remember that in the book Tom looks at Michael and views him asking Carlo to confess as a sign of uncertainty with his decision that Vito would not have.

Another possibility: Michael was trying to find out if other conspirators were involved. Carlo, in his relief in thinking he'd be spared, might have named others if others were involved.

Yes, in the book Tom was a bit surprised by Michael's approaching Carlo and asking him, viewing it as a slight sign of weakness and something the Don would never have done.

Michael knew it was Carlo, but he wanted to humiliate Carlo and make him confess to him with Hagen also present. If he was going to off his brother in law, he was only going to do it after he extracted that confession. Michael was very deft in getting it too. First he gains Calo's confidence by sending him back to the house after the Baptism. Then he terrifies him by telling him the names of all the people who are dead...watch the horror on Carlo's face as Mike recites the names. Then he rants at him about how "that little farce" he played with Connie could never "fool a Corleone." By now, Carlo is really in fear for his life, and Michael switches gears again, and offers him a drink, and tells him his punishment is banishment from the family business, and he makes some comment about making his sister a widow. Then he appeals to him not to insult his intelligence by confessing. He then uses a cross examination technique which basically lays an assumption into a question. Instead of saying "did you do it," he asks "who approached you [to do it]." This breaks Carlo who tells Mike it was Barzini.

Just as a sidebar: When Carlo gets in the car, Clemenza is in the backseat and soon thereafter kills Carlo. Was Carlo a) so distracted about having his life spared that he was not concerned who was in the backseat? b) more relaxed since he knew Clemenza and wouldn't feel as threatened, or c) would have been more apprehensive if an unknown (to Carlo) buttonman was in the backseat?

If Michael wanted to keep the ruse going just a bit longer, should the killer have hidden from Carlo's view until the car started moving? Given Clemenza's, ahem, girth, then maybe he was incapable of bending down and hiding. But certainly someone like Cicci could have.

Just what-iffing here...

But actually there was no need of it... In fact Clemenza started to garrot him immediately, without ceremonies. Long before the car started moving.

The quote that Plaw talked about and that SC posted from the book answers the question. But let's put the book aside for a moment and just go by what we see in the movie itself. In watching that scene I've always took it that Michael was not 100% sure that it was Carlo who set up Barzini. Michael twists the question to Carlo. If Michael had asked Carlo straight out " Did you set up my brother?" he would have shown his hand to Carlo, allowing Carlo to see that there was doubt in Mike's own mind and by seeing the doubt it would have given Carlo an opportunity to deny that he had set up Sonny, with nothing to lose by lying. But by Michael phrasing the question the way that he did to Carlo " Now who approached you, Barzini or Tattaglia?" it tells Carlo " I already know that YOU set my brother up, so there is no denying that, but now I need to know who approached you to set my brother up?" Asking it this way is not showing Carlo that he (Michael) has any doubts that Carlo set Sonny up. Therefore Mike does not let Carlo see his hand and that does not allow Carlo the opportunity to deny it. Phrased in tht manner it makes Carlo confess and at the same time it erases any doubts that Michael had in his own head.


Don Cardi

Michael had to know "it was Barzini all along," especially since his father came to that knowledge beforehand, and it was Barzini who invited Michael to the fateful meeting. So why did he ask Carlo? Perhaps a tactical move: Make Carlo think that by telling the truth, he'd be spared, and so he wouldn't put up a messy fight (or beg for his life) in the compound. Then he'd get in the car to the "airport," and Clemenza could garrot him, neat and clean.
Hell, what differenc