Warning: This article includes one major spoiler to Carr’s The Three Coffins, so don’t read the following if you plan to read the book at some point in the future.
One frequent criticism leveled against Golden Age mysteries almost from the beginning is that they tend to focus on the upper classes and ignore or patronize the lower strata of society. This is of course a cliché, but with more than a grain of truth to it. Golden Age mysteries have been seen to take place in almost every possible milieu but the well-bred always were by far the genre’s favourite class. The trope originated with the Great Ancestors : early detective fiction from Gaboriau to Collins to Green to Doyle also affectioned grand monde settings and characters.
The most obvious reason for that, and the one most often used to dismiss the whole genre, is that Golden Agers were snobs, and this is almost certainly true as far as the British school is concerned. The portrayals of the comparatively few commoners that appear in the novels of the period, especially those by the so-called Crime Queens, leave no doubt about the author’s lack of direct knowledge of and occasional contempt for « The Masses » as they’d probably have put it. Interestingly and somewhat ironically given their later treatment at the hands of historians and critics obsessed with « realism », only the alleged « humdrum » school showed some interest and concern for the lower classes, probably because they felt their stories would be more credible with a suburbian rather than country house setting. As for the American school it also used the rich and famous abundantly but often with a more critical eye, which is probably due to a slightly more politically – if not always socially – liberal slant. Sure there were snobs in the United States too, most often found in what Mike Grost called the « Van Dine school », but overall American mystery writers tended to be much less starry-eyed before wealth and « nobility ».
Exotism – and remember, « Exotism sells! – is another factor playing in this invasion of the blue-blooded. Who are those people? How do they live? How do they die? There has always been a huge market for fiction and non-fiction appearing to answer these pressing questions and most particularly in times of great economic inequality and political insecurity. Most movies made during the Great Depression for instance dealt with people for whom money was not an issue and some genres such as the screwball comedy took place almost exclusively among the (very) well-off. You can thus imagine how popular murder stories set in an apparently protected milieu could and would be. Murder was indeed in a Venetian vase but everyone wanted to peer inside and mystery writers, having to make a living, were more than ready to oblige.
The final reason is paradoxically one of credibility. I say « paradoxically » because the genre is usually thought of as not bothering with issues of realism and verisimilitude, which is only partially true. The kind of stories that the GAD peddled was indeed statistically improbable but not impossible and in some cases premonitory. There have been locked room or impossible murders committed in real life, some of which remain unsolved to this day, and many a cause célèbre has involved wealthy people, proving if needed that being rich doesn’t make you less likely to kill someone else. GAD mysteries in last analysis are not irrealistic but instead focus on a tiny figment of reality, which is not the same thing. The author however has a harder job making their story believable than if they wrote about a shooting in a gang-ridden neighborhood, and every detail must ring if not true, at least possible. The problem is, the standard GAD plot requires a combination of time, dedication, logistics and in some cases materiel that only someone with nothing else to do or care about can carry it out. It takes a retired and well-off intellectual to device something like the extraordinarily complex (so complex that it ultimately fails) murderer’s plan in Carr’s The Three Coffins. It is not a question of common people not being clever enough – it’s a question of them not having the time. If you’re on the dole and badly need money and your aunt stands in the way, you don’t waste hours trying to plan the perfect crime, you just catch a pillow and smother her with it – it’s simpler and probably works better, which after all is the point. « Artists in crime » as they are, the aristocratic murderers in GAD mysteries almost always get caught.