A test to identify a key fact is to ask the question, "If this fact is changed, would the outcome of the application of the law be affected or changed?"

Key facts are the ones that affect a process in a way that they cannot be assessed to change.

Explanation:

Key facts in the suggestion of the name itself means that the facts are the ones that are important to the working of the process that is being talked about.

SO it is evident that any test to identify the key fact is going to assess what the key fact is by seeing the outcome of the application of the key fact in terms of the larger process and how fundamentally it has been affected.

IF it is fundamentally affected then it is evident that it is one of the key facts.

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