Collateral Source" Rule: "This doctrine provides that if an injured party received some compensation for his injuries from a source wholly independent of the tortfeasor, such payment should not be deducted from the damages which the plaintiff would otherwise collect from the tortfeasor." (Hrnjak v. Graymar, Inc. (1971) 4 Cal. 3d 725, 729 [94 Cal. Rptr. 623, 484 P.2d 599, 47 A.L.R.3d 224].) Therefore, the collateral source rule precludes a defendant from presenting evidence that an injured plaintiff's medical expenses have been paid by an independent source. (Helfend v. Southern Cal. Rapid Transit Dist. (1970) 2 Cal. 3d 1, 9 [84 Cal. Rptr. 173, 465 P.2d 61, 77 A.L.R.3d 398].) While the rule may effectively allow a plaintiff to receive a double recovery, " '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. . . . to permit the defendant to tell the jury that the plaintiff has been recompensed by a collateral source for his medical costs might irretrievably upset the complex, delicate, and somewhat indefinable calculations which result in the normal jury verdict. . . .' " ( Hrnjak v. Graymar, Inc., supra, 4 Cal. 3d at p. 730.) Civil Code section 3333.1 modifies the rule with regard to medical malpractice cases. As pertinent, that section provides: "(a) In the event the defendant so elects, in an action for personal injury against a health care provider based upon professional negligence, he may introduce evidence of any amount payable as a benefit to the plaintiff as a result of the personal injury pursuant to the United States Social Security Act, any state or federal income disability or worker's compensation act, any health, sickness or income-disability insurance, accident insurance that provides health benefits or income-disability coverage, and any contract or agreement of any group, organization, partnership, or corporation to provide, pay for, or reimburse the cost of medical, hospital, dental, or other health care services. Where the defendant elects to introduce such evidence, the plaintiff may introduce evidence of any amount which the plaintiff has paid or contributed to secure his right to any insurance benefits concerning which the defendant has introduced evidence. "(b) No source of collateral benefits introduced pursuant to subdivision (a) shall recover any amount against the plaintiff nor shall it be subrogated to the rights of the plaintiff against a defendant." (Fn. omitted.) The effect of this statute has been explained as follows: "The collateral source provision before us . . . is one of the provisions of MICRA which was intended to reduce the cost of medical malpractice insurance. Section 3333.1, subdivision (a) . . . authorizes a defendant in a medical malpractice action to introduce evidence of a variety of 'collateral source' benefits--including health insurance, disability insurance or worker's compensation benefits. Apparently, the Legislature's assumption was that the trier of fact would take the plaintiff's receipt of such benefits into account by reducing damages." ( Barme v. Wood (1984) 37 Cal. 3d 174, 179 [207 Cal. Rptr. 816, 689 P.2d 446], italics in original.) The first paragraph of footnote 5 immediately following this quote sheds more light on the subject. "Earlier drafts of section 3333.1, subdivision (a) required the trier of fact to deduct such collateral source benefits in computing damages, but--as enacted--subdivision (a) simply provides for the admission of evidence of such benefits, apparently leaving to the trier of fact the decision as to how such evidence should affect the assessment of damages." (Barme v. Wood, supra, at p. 179, fn. 5, italics added.) Thus, Civil Code section 3333.1 does not preclude recovery of such damages; rather, it allows the jury to decide how to apply the evidence in calculation of damages.