What is the collateral source rule in the context of a tortfeasor seeking damages from a plaintiff who has invested in long-term insurance coverage?

Liemsakul relies on Helfend v. Southern Cal. Rapid Transit Dist. (1970) 2 Cal.3d 1, 9-10, 84 Cal.Rptr. 173, 465 P.2d 61, for the proposition that a tortfeasor should not garner the benefits of the providence of a victim who has invested years of insurance premiums. ⁸ "The collateral source rule expresses a policy judgment in favor of encouraging citizens to purchase and maintain insurance for personal injuries and for other eventualities" (id., at p. 10, 84 Cal.Rptr. 173, 465 P.2d 61), and averts the perceived injustice in allowing a tortfeasor to take advantage of the thrift and prescience of the victim in having paid the premium. (Ibid.)