Interesting thoughts on the detective story -- I do think that Van Dine's rules are not accepted by the majority of today's readers. They probaly weren't even that widely applicable at the time. What they do, though, is give a framework which to some extent is what makes genre genre.

Mostly, though, I have to bust the Chandler myth. It's fairly clear, in the book, who killed the chauffeur. It becomes confusing, later on, b/c Marlowe lies about it in order to protect his client. Also, TBS, like most of Chandler's work, is "cannibalized" from several older, shorter stories. So the plot has a series of stops and starts; but structurally it actually comes together very well, once you figure out the structure. The film works less well because the censors wouldn't let them use the original solution to the mystery for lots of reasons. And also because most of the exposition got cut in favor of Lauren Bacall in elaborate gowns. Not that I'm complaining, mind.

It's POSSIBLE that Chandler might not have known who killed the chauffeur but more likely (if that story ever actually happened) that he didn't particularly feel like refreshing his memory on something he'd written a decade before that he wasn't getting paid for.