The prima facie inference of causation (breach of duty coupled with injury within the area of foreseeable risk) does not arise where the specific risk that eventuated was not the risk created by the breach, and where the factual matrix makes it impossible for either party to prove or disprove what force caused the damage. A component that fails due to forces it was never designed to bear does not establish causation merely because the component was under-strength, even where the under-strength nature meant it would break sooner under such forces.
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