Being a laptop, it may have a problem with the lid sensor (in the trackpad actually) being glitchy and thinking the lid got closed. I've seen it happen. You could UNPLUG the trackpad outright (and use external keyboard/mouse) as a troubleshooting step.
Another troubleshooting step is "separate hardware from software" by booting the computer off an external hard drive and see if the problem persists or goes away. You can also do the opposite by booting the computer in target mode and booting a different computer off it's startup drive. The latter option has the advantage that you can continue to use it somewhat normally while testing.
If your local "genius" is at all smart they would have done the above tests. Unfortunately, a lot of "geniuses" aren't.
Also the SMC isn't on its own board (AFAIK on any model) so that'd mean a logic board replacement. Not cheap. Being a 2012 they may not even offer that repair. (flat-rate mail-in would probably be cheaper anyway)
Finally, peripherals can cause this. Think anything connected over USB/firewire/displayport/thunderbolt/etc. This includes keyboards and mice
