Though certainly a powerful universal force, Sod’s Law isn't what dictates a dropped smartphone inevitably landing screen down: it is in fact down to the same physics that influences buttered toast in free-fall.
As part of a PR exercise to encourage people to buy its shatterproof phone, Motorola set physicist Robert Matthews to work on the screen-smashing problem (Matthews is best known for his authoritative paper Tumbling toast, Murphy’s Law, and the fundamental constants).
The answer is surprisingly simple: whether a phone lands screen-up or face-up depends on a few variables, mostly how you’re holding the phone at the time of drop and the distance to the ground. Because people tend to hold their phones in a certain way (fingers below the centre of gravity on the back, at roughly chest height), the numbers work out such that phones more often than not land face-down.
The good news is that the equation rests on people fumbling the phone when they drop it: if you just let it go, it’s more likely to land screen-up. Though, I’m not sure that means Professor Matthews will pay you back for repairs if theory doesn’t quite meet reality. For that, you'll probably need that sexy iFixit kit we saw the other day.