concurring.
I concur in the Court’s decision. I think it is important to emphasize that the district court is not foreclosed from considering the admissibility of Dr. Chandler’s affidavits on remand. Our reversal does not mean that the district court’s implicit determination that Dr. Chandler’s affidavits were admissible somehow becomes law of the case and immune from subsequent challenge, whether by way of a motion to strike (the preferred method) or some other form of objection to the district court’s consideration of the evidence. This is important because Dr. Chandler’s opinion as to causation is patently inadmissible.
Dr. Chandler’s first affidavit incorporated an opinion letter dated May 8, 2018. That letter outlined the course of his treatment of Sales’ toe. Dr. Chandler stated that “we determined that it was a mycobacterial infection that was a result from the incident Tracy Sales had at the Salon.” Dr. Chandler’s second affidavit explained: “By use of the word ‘incident,’ I was referring to the presence of mycobacteria in the foot basin in which Tracy Sales received the pedicure at the Salon.” He then explained that the simple exposure to mycobacteria would have resulted in infection, regardless of whether there was some traumatic event in the course of the pedicure: “Tracy Sales[’] toe would have been infected with the mycobacterial [sic] at that time regardless of whether a prick, a poke, or a movement of the cuticle occurred.”
Dr. Chandler reiterated his view of causation in slightly different terms in the first affidavit, stating: “there is a causal relationship between the injuries Ms. Sales sustained and the treatment she received as a result to the incident at the salon in April 2010.” Dr. Chandler’s second affidavit then explained this statement, stating “my use of the word ‘treatment’ ... refers to the placement of Tracy Sales’ feet in the foot basin at the Salon, where her toe became infected with a [sic] mycobacteria.” Dr. Chandler then explained that he held these opinions to a reasonable degree of medical probability.
This presents the critical question: what evidence is there that mycobacteria were present in the basin at the time of the pedicure? There is no direct evidence, in the form of test results or otherwise, that mycobacteria were present in the basin when Sales received the pedicure. Rather, it appears from the definitions that he utilized, that Dr. Chandler held the opinion that mycobacteria were present in the basin at the time of the pedicure. There are only two data points that can be discerned from his affidavits that support this opinion based upon inference: (1) Dr. Chandler’s diagnosis of a mycobacterial infection in Sales’ toe; and (2) Sales’ medical history, in which she “stated she had a pedicure in April 2010 and ‘it has gone downhill from there.’ ”
The lesser problem with reliance on the second datum point is that Dr. Chandler either took an incomplete history as to Sales’ symptoms or elected to ignore the history when he focused on her report that her toe had “gone downhill” following the pedicure. Although she reported that the day after the pedicure, the toe was “sensitive, and red, and puffing up” these symptoms quickly disappeared. It was only some months later that she began to experience pain “in a totally different aspect.” Thus, although Sales experienced initial inflammation in the toe following the pedicure, this symptomology resolved for a period of some months before her more serious symptoms emerged. Given that the sole connection that he identified between the infection and the pedicure was Sales’ description of her symptoms, Dr. Chandler’s failure to address the significant period when Sales was asymptomatic raises significant questions as to the reliability of his inference that the basin was infected with mycobacteria.
The greater problem that I have with Dr. Chandler’s opinion is the methodology upon which his opinion is based. This Court, until recently, rejected mere temporal coincidence as a basis for expert opinion testimony as to causation.3 Coombs v. Curnow, 148 Idaho *205129, 141, 219 P.3d 453, 465 (2009); Weeks v. E. Idaho Health Servs., 143 Idaho 834, 839, 153 P.3d 1180, 1185 (2007); Swallow v. Emergency Med. of Idaho, P.A., 138 Idaho 589, 594-95, 67 P.3d 68, 73-74 (2003). However, this Court recently adopted a more expansive view of the admissibility of expert testimony as to causation in Nield v. Pocatello Health Servs., Inc., 156 Idaho 802, 332 P.3d 714 (2014).
I raise the decision in Nield, not because I wish to rekindle disharmony among the members of this Court, but rather because I am concerned that the district court may view itself as constrained by that decision to hold that Dr. Chandler’s opinions are admissible. In Nield, this Court held that the district court erred when it determined that the expert opinion testimony regarding causation proffered by the plaintiff was inadmissible. Id. at 817, 332 P.3d at 729. This Court did so, despite the dissenting justices’ views that the opinions were “based upon the temporal relationship between Ms. Nield’s admission to PCRC and the onset of her infection.” Id. at 822, 332 P.3d at 734. (Eismann, J., dissenting).
The central dispute between the majority and the dissent in Nield was the significance of our holding in Weeks and that decision’s reliance on a federal case, Clausen v. M/V New Carissa, 339 F.3d 1049 (9th Cir.2003). The majority clearly rejected a line of authority from the federal courts regarding expert opinions of causation, stating “Being the highest court of a sovereign state, we are free to adopt our own concept of differential diagnosis and we decline to follow the more expansive definition employed by some federal courts.” Nield, at 810, 332 P.3d at 722.
The majority continued: “[T]he district court erred here in holding that expert medical testimony was required in order to establish how and where Nield was infected. This Court’s concept of the differential diagnosis methodology does not require such a holding.” Id. at 813, 332 P.3d at 725.
These statements were made in evident response to the dissent’s view that:
the rule regarding differential diagnosis adopted in Weeks was not simply to diagnose what medical condition was causing the patient’s symptoms. It was, as in Clausen, to determine the reliability and admissibility of an expert’s opinion on the issue of proximate cause in a negligence action. In fact, in Clausen it was used to determine the reliability and admissibility of an expert’s opinion as to the proximate cause of an infection, which is precisely the issue to which the district court utilized differential diagnosis in this ease.
Id. at 827, 332 P.3d at 739 (Eismann, J., dissenting).
However, I do not believe that the decision in Nield controls the district court’s decision as to the admissibility of Dr. Chandler’s decision on remand. In Nield, the majority quoted from the affidavit of the plaintiffs expert physician, who in turn quoted a letter from the Idaho Department of Health and Welfare directed to the defendant: “ ‘There were four or five other residents in rooms near the identified resident with methicillin resistant staphylococcus aureus infections.’” The findings of the investigation confirmed and substantiated poor infection control measures by the staff. Id. at 845, 332 P.3d at 757. In short, in Nield, there was an *206abundance of evidence as to the defendant’s poor infection control measures and at least a modicum of evidence that would support an inference that the plaintiff had been exposed to the organism that led to her infection. Thus, the majority held that Nield had presented sufficient evidence to support a finding of the existence of a “chain of circumstances from which the ultimate fact required to be established is reasonably and naturally inferable.” Id. at 812, 332 P.3d at 724 (quoting Sheridan v. St. Luke’s Regional Medical Center, 135 Idaho 775, 785, 25 P.3d 88, 98 (2001)). Based upon this conclusion, the majority held that no expert testimony was required.
Unlike Nield, on the record presently before this Court, there is simply no evidence giving rise to a reasonable inference that mycobacteria were present in the basin at the time of the pedicure. Thus, unless Sales can adduce additional evidence that would support an inference of mycobacterial presence in the basin, the district court would be wholly justified in striking Dr. Chandler’s affidavit for want of foundation and dismissing this action.
. This rule applies to expert testimony. It does not apply when lay opinion would be admissible, i.e., when:
*205such causation is within the usual and ordinary experience of the average person, and also satisfies I.R.E. 701. For example, if a person fell down some steps, landing on a knee, and immediately thereafter felt pain in the knee, saw an open wound on the knee, and within minutes or hours observed that the knee was swelling, that lay person could provide reliable testimony that the pain, wound and swelling were caused by the fall.
Dodge-Farrar v. Am. Cleaning Servs. Co., 137 Idaho 838, 842, 54 P.3d 954, 958 (Ct.App.2002).
However, as the Court of Appeals cautioned:
As the claimed symptoms and treatment become more separated in time from the fall. however, the causal relationship becomes more doubtful and tenuous, and expert testimony becomes necessary to establish causation. As time passes, the possibility that prior or subsequent injuries or unrelated disease processes may play a causal role makes lay opinion unreliable and inadequate to sustain a claim.
Id. at 842-43, 54 P.3d at 958-59. The passage of time and resolution of Sales' symptoms in this case clearly foreclose the admissibility of a lay opinion that the infection was caused by the immersion of her foot in the basin or that the water in the basin contained mycobacteria.