The Watts v Rake / Purkess v Crittenden evidentiary onus on a defendant applies where the issue is whether the causal connection between an accident and continuing disabilities has ceased, not only where the issue is whether a pre-existing condition would independently have led to incapacity. Medical evidence that evolves as more information (such as surveillance footage) becomes available, and which ultimately opines that the causal relationship has ceased, is capable of discharging that evidentiary onus. The ultimate burden of persuasion on the balance of probabilities remains on the plaintiff throughout.
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