Much harder to stage an accident than it looks, I think. There are rarely any climbable heights to push someone off of, and pushing someone off a 20 foot tall boulder is an iffy way to cause their death. The murderer would have to cover any traces of themselves being at the top of that rock (including DNA). The very fact of being on top of an outcropping would make the scene visible and you can see a long way in the desert. ATV riders, mountain bikers, target shooters...can all be out there.
Anyway, most places in the Mojave don't have immediately drop offs, but look very much like the Granite Hills, so the person would bounce and scrape (and possibly come to rest badly injured but not dead; the perp could let them die but that would be obvious to a coroner).
A person who was given a really hard shove would have a different bounce pattern than someone who slipped (but a person who was suicidal and jumped might look a lot like a murder victim, I think). If foul play is expected (and sometimes even when not) they do examine the fall area for blood, to try and reconstruct what happened. I can remember this really awful time in Sequoia when two young men fell from Moro Rock during an ill-advised attempt to climb off its nose (without climbing equipment). They sent a helicopter with a person dangling and a kind of basket thing for body part retrieval, but they also examined the rock (out of interest, I think - the coroner's report ultimately mentioned such things as the length before first impact).
Contriving to lead someone someplace and then abandoning them might work. In so many couples and especially in groups, only one person is paying attention to the actual route (in most cases when I hike, that would be me, and if someone else was doing the route finding, I'd still have a map and I'd still memorize my own route, but lots of people go right across small intersecting trails without noticing, because they are all into staring in wonder at the land around them).
But I could envision someone saying "Let's go on a short walk" and then making sure it was a much longer walk, with many turns onto other trails, then the leader suddenly vanishes (pretense of going to pee?) and that's it for the other person.
Or the walk could just be much further than the leader knows the follower can really handle (or has gear to handle).
Anyway, pushing someone off even a 45 degree slope in the Mojave isn't going to kill them, they're going to roll and get stuck (and still be quite visible from the air, I'd think). You'd need to get to a good sized canyon. A few people have murdered their spouses at Grand Canyon...and it's possible that some have done it and gotten away with it. At least one man murdered his wife near Tunnel View in Yosemite, too, by pushing her off a trail.