"Russia's actions in this situation cannot in any way be said to be hostile to Turkey," said Kapustin, President of the Russian Association of International Law.
"Even if the Russian plane flew into Turkish airspace and returned to Syria, it needs to be taken into account that the Russian air force is taking part in an armed conflict in Syrian territory, on the side of the central government."
"We are factually and legally participants in that conflict, that is, subject to the Geneva conventions and protocols."
Russia's Su-24M Fencer bomber jet evidently posed no danger to Turkey, even if it had crossed into its airspace, making Turkey's action all the more unreasonable, said Kapustin.
"That Turkey, as is being said, used a weapon, that is quite strange, even in the context of an armed conflict – to shoot a plane above your territory, which has not taken any threatening actions, is a very harsh measure to stop an airspace violation."
"Incidents happen all the time, there are loads of these situations, not only in zones of conflict, but in ordinary border situations."
"As a rule, all incidents of a military kind, using military force, are resolved by a special commission, which establishes the facts, checks documents, and then makes a decision about who is at fault and to what extent they must pay damages."
"That is the usual scheme for this kind of situation," said Kapustin, adding that if those involved cannot come to agreement on the facts, then "the parties may hand over the case to a third party, who will decide who is right and wrong."