Did Russia murder the Polish government?

In April 2010, senior members of the Polish government, including the Polish president and first lady, got on a plane to head to Smolensk, Russia, to commemorate the 70th Anniversary of the Katyn Massacre, in which Josef Stalin ordered the murder of 20,000 Polish army officers and other intelligentsia and had them buried in the Katyn Forest, outside Smolensk, in an attempt to decapitate Poland in preparation for installing a post-war communist regime.

This was one massacre for which the Nazis, who discovered the mass graves in the Katyn Forest, were not responsible, though they, too tried to decapitate Poland by killing its intellectuals.  The Nazis conducted a very public investigation, witnessed and vouched for by the Red Cross, that fixed guilt for the massacre on the Soviet Union.  Stalin denied in, blaming Germany.  Roosevelt and Churchill stayed silent, not wanting to alienate their ally.  Arguably no country suffered more in World War II than Poland.

The 70th Anniversary was to witness a very public admission by the Russians (they had only admitted responsibility in 1995) for the massacre.  A very, very big step for them, though, one might say, out of character for Vladimir Putin.

But the Polish plane never arrived.  Instead, it crashed under mysterious circumstances outside Smolensk.

Sound suspicious to you? It did to me at the time.  And Russia's behavior in "investigating" the crash has only added to those suspicions.  The Washington Examiner's Diana West:

What really happened in the forests at Smolensk, Russia, when a Polish aircraft carrying Poland's national leadership crashed in April 2010, killing all 96 people on board, including Poland's president and first lady?
The answers Russia presented to the world in its official 2011 crash report are wholly unsatisfactory. Indeed, the Moscow-controlled crash investigation seems to have been designed to suppress or tamper with evidence to exonerate Russia of all responsibility for an accident -- or guilt for a crime.

[...]
The Russians assert that Polish pilot error, induced by pressure to land supposedly by the Polish president himself, caused the crash. Poles, particularly those associated with the late president's conservative Law and Justice party, see something far more sinister.
In this worst case scenario, Russian air controllers incorrectly informed Polish pilots they were on the proper glide path when that wasn't true. On purpose? If so, the world has witnessed the mass assassination of a government. And done nothing.
I don't claim to judge the evidence. But it's clear an impartial investigation is warranted because of a Moscow-run investigative process marked by irregularities. These include the red flag of a fact that Russia has refused to return the black boxes of the Polish plane to Poland.
Other irregularities, as summarized in a November 2011 Polish document known as the Smolensk Status Report, are that crash evidence was crudely destroyed (including by bulldozers), tampered with, and lied about (Russian investigators claimed no radar video recording existed, for example, but then cited it in the report). The document notes some Russian pathological reports on victims included descriptions of organs that had been surgically removed before the crash.
A glaring discrepancy concerns the cockpit voice recording. To prove the pilots were under third-party pressure to land, the Russians reported a Polish crew member twice says "He will go crazy" if the plane doesn't land.
Both the Polish Investigation Committee and the Polish Prosecutor's Office publicly contended no such statement was made, and that the Russians altered the CVR to create the statement.

Unfortunately, until and unless Putin is removed from power and a more honest government installed in his place, I doubt we will get to the bottom of this incident.