Judith Busсaglia (“Buscaglia”) slipped and fell in a United States Post Office in Elm-hurst, Illinois, on January 27, 1987. Nearly four years later, she filed a complaint in federal district court seeking $250,000 damages against the United States (“the government”) under the Federal Tort Claims Act (“FTCA”). 28 U.S.C. § 1346(b). The government filed a motion to strike the affidavit of Buscaglia’s expert, John Van Ostrand, and a motion fоr summary judgment. The district court granted both motions. Buscaglia appeals those rulings. We affirm in part and reverse in part.
I.
On the evening of the incident giving rise to this litigation, the ground outside the post office was covered with a thin layer of snow and slush. Buscaglia was wearing snow boots as she entered the post office, crossed wet floor mats, and walked through a vestibule and across the lobby to deposit her letters. While returning across the lobby, Buscaglia slipped and fell approximately four to six feet from the vestibule. She noticed a muddy accumulation of water in the area of her fall.
The postal facility’s established policy required an employee to examine the lobby floor, on days of inclement weather, at approximately fifteen minute intervals and to mop up standing water when necessary. According to the depositions of postal employees, the post office janitor, Gene Hillard (“Hillard”), routinely mopped the area of the *532 lobby where Buscaglia fell. 1 He last checked the lobby area at 5:55 р.m. that evening. Hillard told another postal employee, John Anderson (“Anderson”), that the lobby was “fine” and proceeded to “punch out” for the day.
Buscaglia asserts two theories that would entitle her to recover under the Federal Tort Claims Act. First, she claims that the government negligently surfaced the floor with tile it should have known would becоme “unduly slippery when wet.” In support of this theory, Buscaglia offered the affidavit of John Van Ostrand, a licensed architect and expert on the slip resistance of floor tile. Second, she contends that the government negligently failed to exercise ordinary care in removing tracked-in water from the post office lobby after vоluntarily undertaking that task. After first granting the government’s motion to strike Van Ostrand’s affidavit, the district court granted summary judgment for the government on both theories of liability. Buscaglia appeals all of the district court’s rulings.
II.
We first consider whether the district court erred in excluding Van Ostrand’s affidavit under Fed.R.Evid. 403 and 702. In response to Buscaglia’s discovery request, the government рrovided a sample piece of tile 2 upon which Van Ostrand performed three independent tests to ascertain its coefficient of friction—a measure of a surface’s slipperiness. According to his affidavit, these tests are generally accepted, widely used by professionals, and based on long-established scientifiс principles. ’ Applying these tests, Van Ostrand determined that the tile sample had a coefficient of .32, which fell below the commonly accepted level of .5 for slip resistant surfaces in buildings accessible to the public. 3 Based on this calculation, Van Ostrand opined that (1) even when dry, the floor surface was improper for a рublic building, and (2)’ when wet, the floor surface was even more dangerous because its co-efficient of friction would be lower still.
A trial court has broad discretion in ruling on the admissibility of expert testimony, and we will reverse its decision only in the case of a clear abuse of discretion.
Wallace v. Mulholland,
On appeal, Buscaglia concedes the obvious—that the average person comprehends thаt floor surfaces become more slippery wet than dry. She maintains, however, that Van Ostrand’s expert testimony was admissible under Rule 702 to explain that some surfaces’ *533 slipperiness increases more than others and to establish that the floor surface of the Elmhurst Post Office did not meet the appropriate standard for a public building. Furthеr, she argues that the court’s decision to exclude the affidavit under Rule 403 was manifestly erroneous. Buseaglia insists that the court vastly understated the probative value of Van Ostrand’s affidavit by overstating the differences between the test sample and the condition of the floor on which she fell, in part because the court based its decision on faulty premises not supported in the record.- Specifically, Buseaglia asserts that the record evidence indicates a dispute as to whether the floor was wet or dry at the time of the fall—she claims that the floor was wet while two postal employees gave deposition testimony that it was dry. . In addition, Bus-caglia points оut the absence of testimony indicating when the floor previously had been waxed and with what type of wax.
As a threshold matter, Van Ostrand’s affidavit could be admitted only upon the laying of a foundation that the tests he performed on the tile sample occurred under substantially similar circumstances to those present at the time of the aсcidént.
Estate of Carey by Carey v. Hy-Temp Mfg., Inc.,
Rule 702 establishes two admissibility requirements for expert testimony: (1) the expert must be qualified, and (2) the subject matter of the expert’s testimony must be suitable, that is, consist of specialized knowledge that will be helpful or essential to the trier of fact in deciding the case correctly.
United States v. Stevenson,
Of cоurse, expert testimony that is otherwise admissible under Rule 702 may nonetheless be excluded under Rule 403 if its probative value is outweighed by the danger of unfair prejudice.
United States v. Brown,
In sum, the district court committed clear error by critically discounting the probative value of Van Ostrand’s affidavit while significantly overstating the risk of prejudice and confusion its admission would engender.
III.
In reviewing the district court’s grant of summary judgment to the government, we examine the record and the controlling law
de novo. Apple v. West,
The substantive law of the state where the injury occurred governs actions brought under the Federal Tort Claims Act.
See Hess v. United States,
[I]t was a jury question as to whether the defendant knew or should have knоwn that the material used in the composition of the floor, upon becoming wet and damp, became very slippery and dangerous.... It is this feature of the condition of an outside terrazo [sic] floor which distinguished this case from those cases in which recovery has been denied as a result of slipping and falling on a wet floor.
We find that Van Ostrand’s affidavit and deposition testimony present a sufficient factual basis such that a trier of fact could find for BuscagUa on the theory that the composition of the floor, either by itself or in combination with an accumulation of water, caused her injury. 5 Accordingly, we reverse the district court’s grant of summary judgment on her first theory of UabiUty. Of course, whether the evidence should result in judgment on the merits for BuscagUa is another matter altogether, on which it is not our role to comment.
Finally, we address BuscagUa’s argument that the government, having undertaken the task of removing the natural accumulation of water in the lobby, failed to meet the appücable standard of ordinary care.
See Wilson v. Gorski’s Food Fair,
IV.
The district court erred in excluding the affidavit of John Van Ostrand under Fed. R.Evid. 403 and 702 and in granting summary judgment for the government on Bus- *536 caglia’s first theory of liability while it properly granted summary judgment fоr the government on her second theory of liability. Accordingly, the judgment of the district court is AFFIRMED IN PART, REVERSED IN PART, and the case is Remanded for proceedings consistent with this opinion.
Notes
. Hillard's deposition was never taken.
. The floor tile in the Elmhurst Post Office has been identified as "Kentile 1071, 1J 243B Earth and Brown Rustic Stone.” The government provided the sample piece of tile from its replacement stock.
.Aсcording to Van Ostrand, this standard was promulgated by the Capital Development Board of the State of Illinois.
. The court specifically noted examples of how plaintiff might have.presented evidence supporting her allegations: "For instance, a custodian of the building could have explained how often the foyer was waxеd and buffed. A building contractor could have testified whether the ceramic tile used in the building was reasonably safe or excessively slippery. Even plaintiff could have detailed the factual basis for his conclusion that the foyer was too slippery.”
Id.
. It remains for the trier of fact to resolve the factual dispute as to whether the flоor was wet, as Buscaglia claims, or dry, as the postal workers assert in their depositions.
. As noted, Hillard was not deposed although he could have shed light on whether he actually mopped the area in which Buscaglia fell. Of course, Buscaglia had the right to depose Hillard or to apprise the court of the reasons she was unable to do so. Having done neither, Buscaglia may not escape summary judgment on the possibility that a witness may come forward at trial to establish her right to recover.
