The US and Russia both would have eavesdropping intelligence about the radio communications from both sides.
There is, no doubt, satellite surveillance of the area particularly after the Russian airliner shootdown.
What will show the truth is Russia's response. Typically they bluster and take a hostile posture as their first reflex. If Russia backs down (goes quiet) within the next few days, I think the evidence supports Turkey's claims.
Make no mistake, Turkey still has a problem either way. Russians never forget and will exact some form of retaliation.
I dont give a damn in Russia flew through Turkeys airspace to attack terrorists!
The government of Turkey just MURDERED two Russians because they had to gall to fly through Turkish airspace while KILLING TERRORISTS!
If I were Putin... I would be bombing the Turkish capital!