Who's Scott Ritter's source? I've heard his logic. The argument is this:

• The S-300 system launched the missile. It is definitively Ukrainian and we can prove that forensically. That's not in doubt.
• The S-300 would realistically be fired east at incoming missiles or aircraft coming from Russia. This missile's trajectory went west. This could have been a malfunction or a deliberate act.
• In order to fire an S-300 system, you must paint a radar target in the sky that the missile will track. This is the incoming aircraft or missile which is to be shot down. However, you could fire it at a painted target that is stationary (a drone) in order to get the missile to travel on a ballistic trajectory towards Poland. You would need an additional person or team to supply this target to make this work.
• Ukraine has made no effort to investigate, and a Ukrainian general overseeing the air defense systems claims there was no malfunction. There was no error.

Therefore, Ritter believes the missile was deliberately fired at Poland in an attempt to create a false flag and compel NATO to war with Russia. I don't know enough to evaluate this theory. I'll have to defer to someone else with expertise. However, it should be noted that Ritter was a professional weapons inspector. This is his field of expertise.

Also, as an aside, technically, this means NATO has an obligation to defend Poland from Ukraine, not to defend Ukraine from Russia.