I do know some have successfully muddied the waters ( threats of legal action etc ) but to be honest generally speaking once a JC committee is formed, you pretty much are toast. It's all over.
This is correct. There is a lot of confusing info in this string.
You should be specifically told if this is a "Judicial Committee" that you are asked to attend. If they Elders have already decided to convene a JC, then they believe that they already have the required evidence to DF, typically 2 witnesses to 1 event (but seen or heard by 2 different people) or 2 witnesses to 2 different similar events (if you talked to 2 people about apostasy at different times).
IF they do NOT have sufficient evidence to DF, then they will typically form an "investigative committee" usually of just 2 elders and meet with you hoping you confess to what has been reports by perhaps just 1 person.
You should specifically ask the purpose of the meeting. Is it a JC?
If it is NOT said to be a JC -- just a "friendly call" to discuss something or to encourage you or whatever blah blah blah they say, you can refuse without risk.
However,if it is already to the point of a JC, and you refuse to attend, you can still be DFd in absentia, because they are convinced they have 2 witnesses to justify the action.