In order for a hypothesis to stand the test of scrutiny, one must consider who had the means, motive, and opportunity, and the following questions must be satisfied:
1) Who?
--Putin & Tusk
2) What?
--Assassination by plane crash
3) When?
--Known
4) Where?
--Smolensk airport
5) Why? (The "why" also answers the "who." Strong motive usually points to perpetrator.)
Power & revenge--usually the strongest motivators in political assassinations. Here is who would benefit most and why:
"Tusk-A friend to Russia?"
"Polish Plane Crash Boost PM Tusk" (Motive: power)
"Polish premier's ill-fated trip shrouded in acrimony" (Acrimony over how to deal with Russia. Tusk=pro-Russia, Kaczynski not. Motive: power & revenge. Also, very convenient that Tusk had been "invited" several days earlier alone.)
"Poland PM Tusk Considers Running for President" (Motive: power)
"Poland's air crash also killed a swathe of the country's elite" (Consider their accomplishments and ask, "Did they help or hinder Russia?" Motive: revenge)
"Scent of shale gas hangs over Katyn" (Motive: Money & power)
"Poles wary of Nord Stream pact" (Note pipeline originally planned directly from Russia to Germany)
"Nord Stream Ensures Unrestricted Access to Polish Ports" (March 5, 2010-route change press release. Now possible from Russia to Poland. Motive: power...keeping Poland "in line" with gas supply or else cut off like in Ukraine. Remember Kaczynski was pro-West and Tusk much more pro-Russia).
"Analysis: Polish euro dream still elusive after crash" (It's better for Russia if Poland does not go Euro-keeps Poland more isolated from West. Easier to manipulate and strong-arm Poland.)
" The death of Poland's president carries a terrible echo of his country's past" (Illustrates how much of a thorn in the side of Putin Kaczynski really was.)
"Redzikowo Missile Defense Shield" (More pain-in-the-ass for Russia, part of revenge motive)
"Polish President Kaczynski was nationalist, pro-U.S" (Motive: more revenge)
"Diplomats mull practical impact of Polish air disaster" (Reasons for elimination of Kaczynski and key party players who were pain-in-the asses for both Putin & Tusk)
And, last but not least-
"Throughout history, Russian leaders have sought to suppress dissent by driving critics into exile - or worse"
6) How?
Plane was overhauled just several months earlier in Russia. Opportunity for sabotage. (This is both the "means" and opportunity")
Ex-lieutenant colonel of KGB is expert in plotting and carrying out assassinations. That is part of their training, as is suppression of information (propaganda expert) and "damage control." (This is the "means" portion.)
And let us not forget, exaggerated reports of fog (if it was really so bad, why wasn't the airport closed due to weather, as is standard procedure) as well as gunshots at Smolensk crash site. Most logical explanation for gunshots is that Russian soldiers were either dispatched or lying in waiting to prevent intrusion by witnesses and to ensure control of evidence. Those are indeed gunshots from a hand-gun. I played this video for a couple of guys who served in the army-they confirmed. Ammunition blasting off spontaneously from heat and fire sound different, more erratic and hollow. Note especially first shot in video. Unmistakable gun-shot, with echo. Remember, Russian guy in video is close enough to distinguish which is reason for his panicked cursing.
...
Also remember reports of Polish officials initially being barred/physically restrained from access to crash site (shown below), and reports of Polish complaints concerning lack of information.
"That probe is moving fairly quickly, aviation experts said, but some Poles have complained about a lack of public information, including the transcript of conversation in the cockpit before the accident.
Jerzy Artymiak, spokesman for Polish military prosecutors, said one of three black boxes found will be brought to Poland...while the other two continue to be examined in Russia."
You would have to be completely lacking basic critical thinking capacity not to seriously consider this as justifiable means, motive, and opportunity.
Photo of Russian officials restraining Polish investigators