Re the murder of Boris Nemtsov, it's worth bearing this in mind:
Nemtsov’s allies were divided on whom to blame for the murder. Some pointed a finger at the Kremlin, since the crime took place literally just outside its walls, swarming with guards and security cameras. Others suspected the hand of rogue zealots like the Moscow-born former east Ukraine militia leader Igor Strelkov, who returned from Donetsk vowing to wage war against a “fifth column of national traitors” first identified by Putin.
But that speculation is pointless, because we’re never going to find out.
Unless we've been taking happy pills and are assuming that the investigation will be conducted competently and will go wherever the evidence takes it, then politically, the interesting thing here isn't who killed Nemtsov, but who is going to get blamed (and probably, though not necessarily, framed) for it.
It may, for instance, be the right time to rein in people like Streltsov and the ultra-nationalists who have been getting a bit over-inflamed - a bit too prone to independent action - since the whole Ukraine thing kicked off. This would have the advantage that nationalist crazies are indeed likely suspects and so the drive to let them know who's boss would be bolstered by a more or less legitimate investigation. Of course, this raises the issue of whether Moscow can, in fact, get the crazies to wind their necks in.
Early doors, the regime has floated the idea that Muslim terrorists might be responsible, implying that - because Nemtsov was Jewish - his murder was an anti-semitic attack similar to that perpetrated after the Charlie Hebdo murders. This has the advantage of tying into one Russian propaganda line - 'why the hostility, we're all facing the same threats?' - while satisfying the Russian overclass penchant for brutal mockery. When it comes to offensive humour, Charlie H has nothing on those guys.
Another early attack line was that it was a 'provocation', ie that the opposition movement murdered one of its most prominent members in order to revive its fortunes. If this line is followed, it would indicate either that the regime thinks that the opposition are more of a threat than observers tend to think, or contrariwise that authoritarianism in Russia has metastasized to the point where even basically symbolic non-sistema opposition is not tolerable. Lots of opportunities here to fling all sorts of allegations and kompromat around. Also, the National Bolsheviks could be fit into this frame quite neatly, them being actual dingbats and everything.
Lastly, there's the dead bat option: put it down to his private life. Something connected with his sex life, for instance, or maybe someone he lent money to who thought it cheaper to hire a hit squad than pay the debt back. Again, lots of potential for smearing the opposition, though the main political takeaway would be that the regime considers Nemtsov's murder to be part of an acceptable status quo. Nothing to see here but the dead guy. Draw your own conclusions.
*definition of dietrologia here. To my mind, it doesn't really do justice to the actual situation in Russia (or Italy for that matter. Or China). After all, Nemtsov almost certainly was murdered as a result of a conspiracy of some sort. In Moscow, we're all dietrologicians.