Slaughter, J.
The amount of evidence necessary for a court to instruct a jury on a mitigation-of-damages defense is minimal, requiring only a “scintilla”. This stands in contrast to the preponderance-of-the-evidence standard required to prevail on the defense. Here, there was enough evidence to support giving the challenged instruction. We grant transfer and affirm the trial court.
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Trial courts generally enjoy considerable discretion when instructing a jury. Wal-Mart Stores, Inc. v. Wright, 774 N.E.2d 891, 893 (Ind. 2002). When a party challenges a trial court’s decision to give or refuse a proposed jury instruction, a reviewing court considers three things:
• Does the instruction correctly state the law?
• Is the instruction supported by evidence in the record?
• Is the instruction’s substance covered by other instructions?
Id. Only the first consideration is a legal question on which the trial court receives no deference. The other two are reviewed for an abuse of discretion. Id.
This case is about the second consideration: the amount of evidence needed to instruct the jury. We have set the evidentiary bar deliberately low because our constitution guarantees the right to a jury trial in both criminal and civil cases. Ind. Const. art. 1, §§ 13(a), 20. Consistent with these rights, “[a] party who makes a proper request is entitled to have an instruction based upon his own theory of the case if within the issues and there is any evidence fairly tending to support it.” Lavengood v. Lavengood, 225 Ind. 206, 211, 73 N.E.2d 685, 687 (1947) (citing Carpenter v. State, 43 Ind. 371, 373 (1873)) (emphasis added). This “any evidence” standard applies to instructions for both claims and defenses. See id. at 210–12, 73 N.E.2d at 687 (discussing plaintiff’s instructions to support his claim); Indianapolis Horse Patrol, Inc. v. Ward, 247 Ind. 519, 525, 217 N.E.2d 626, 629 (1966) (noting defendants’ instructions to support their qualified-privilege defense).
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We turn next to the affirmative defense at issue here—failure to mitigate damages. Our leading case on this defense is Willis v. Westerfield, 839 N.E.2d 1179 (Ind. 2006), a personal-injury case. There, we explained that tort plaintiffs must mitigate post-injury damages; otherwise, the damages they can recover are reduced “by those damages which reasonable care would have prevented.” Id. at 1187 (citing Kocher v. Getz, 824 N.E.2d 671, 674 (Ind. 2005)). Thus, a plaintiff’s failure to mitigate damages is not an affirmative defense to liability; it merely reduces the damages the plaintiff may recover. Id. In other words, the defense concerns not a defendant’s liability but a claimant’s actions or omissions that worsen the claimant’s injuries. Id.
The defense has two elements, and to prevail the defendant must prove each element by a preponderance of the evidence. Id. at 1188. The first is that the plaintiff did not exercise reasonable care in mitigating post-injury damages. Id. The second is that the failure to exercise reasonable care caused the plaintiff to suffer harm beyond that attributable to the defendant’s negligence. Id. When the defense is that the plaintiff did not follow medical advice, thus aggravating his own injuries, the defendant must prove the plaintiff’s neglect caused him “to suffer a discrete, identifiable harm arising from that failure, and not arising from the defendant’s acts alone.” Id.
Proving such causation often will require expert medical testimony, but not always. Id. In Willis, we rejected a bright-line rule that would have required expert testimony across the board. Instead, we held that whether to give such a failure-to-mitigate instruction must be decided on a “case-by-case basis.” Id. at 1189. In each case, after the close of evidence, the trial court must determine whether the defendant “produced enough evidence of causation” to support an instruction on the mitigation-of-damages defense. Id. In answering that question, the court should consider whether the medical issue is within the “common experience, observation, or knowledge of laymen.” Id. (citation omitted). “If it is, and the defendant has produced competent non-expert evidence of causation,” then the lack of expert testimony “does not preclude an instruction on failure to mitigate.” Id.
Last, we consider whether the court below erred by instructing the jury on the failure-to-mitigate defense. Humphrey’s only objection is that the instruction is not supported by the evidence. We disagree and hold there was no error because the instruction finds support in this record.
Here, as in Willis, the failure-to-mitigate defense is based on Humphrey’s having ignored the advice of his treating physician….
Recall that Humphrey’s theory of the case is that a preexisting pituitary tumor became “apoplectic”—it swelled—due to trauma from the accident. According to Humphrey, the trauma caused physical symptoms for which he sought damages, including “acute vision loss” and elevated prolactin levels that led to truncal obesity, fatigue, and low libido. On the issue of damages, defendants argued that to the extent their negligence harmed Humphrey, he did not exercise reasonable care in mitigating that harm. And they pointed to evidence in the record that Humphrey’s own failings either aggravated his injuries or prolonged them. In other words, defendants say, Humphrey would have suffered less had he done more.
We agree with Tuck and U.S. Xpress that there was sufficient evidence to support instructing the jury on their defense of failure to mitigate damages. As to Humphrey’s vision, he testified that he had no vision problems before the accident. Since the accident, he complains of vision problems that, he says, limit his ability to drive a vehicle; make it harder for him to see at night, especially if it is raining; and affect his ability to read signs and see peripherally. Yet even with these vision issues, Humphrey has not worn corrective eyeglasses or contacts—despite having a prescription for glasses that he never filled. For the past year, he did not return to the optometrist to get a new prescription, despite acknowledging that new glasses “may” help his vision. And he conceded that he made an appointment to see an optometrist about getting new glasses for his eyesight. Under our minimal standard for instructing the jury, this is enough evidence to allow a lay jury to consider whether Humphrey’s vision would have improved had he either filled an existing prescription for eyeglasses or obtained a new prescription.
As to Humphrey’s hormonal imbalance, the record shows that Dr. Stachura prescribed bromocriptine to reduce Humphrey’s prolactin level. This level, if left untreated, can cause or exacerbate testosterone-related issues, including the low-energy issues of which Humphrey complains. Yet Humphrey did not immediately begin taking bromocriptine. Later, when he took it consistently, “his prolactin levels had decreased significantly.” Humphrey, 132 N.E.3d at 516. But Stachura also testified that Humphrey stopped taking the bromocriptine because of nausea, that Humphrey was told to follow up to fix the problem, but that he did not. Once Humphrey eventually began the alternative treatment of testosterone injections—a year and a half after stopping the bromocriptine—his symptoms improved. When asked on cross-examination whether the testosterone injections were helping, Humphrey said they “help[ed] in a lot of ways”, and that he had already noticed improvement. As with Humphrey’s vision, this evidence, viewed most favorably for defendants, would allow a reasonable juror to conclude that Humphrey’s continuing symptoms qualified as an identifiable harm attributable not to defendants’ negligence but to his failure to follow his doctor’s orders. No more is required to instruct the jury.
Our opinion in Willis teaches that a defendant is entitled to a failure-to-mitigate instruction if the evidence would support a finding that the plaintiff’s own actions or omissions failed to mitigate his own harm by any “quantifiable amount or specific item.” 839 N.E.2d at 1190. The requirement of a “quantifiable” harm does not mean the defendant must prescribe a specific numerical value to the plaintiff’s increased or prolonged harm. The respective burdens on plaintiffs and defendants are symmetric—a defendant’s burden is no greater than a plaintiff’s. Just as Humphrey did not need to quantify his request for damages to any degree of mathematical precision, neither did Tuck and U.S. Xpress need to do so on their defense. In both cases, it was up to the jury to determine whether, and to what extent, Humphrey was injured due to the defendants’ negligence and, likewise, whether, and to what extent, Humphrey failed to mitigate his own damages.
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For these reasons, the trial court did not abuse its discretion in giving the failure-to-mitigate instruction. Thus, we affirm its judgment, including its denial of Humphrey’s motion to correct error.
Rush, C.J., and David, Massa, and Goff, JJ., concur.