Testimony of the Biomechanical Engineering Expert Witness About the Dangers of Inclined Sleepers Limited
Posted on December 30, 2024 by Expert Witness Profiler
For over 10 years, Fisher-Price sold a product called the Rock ‘n Play Sleeper (RnP). The Plaintiff, Ameena Brown, argued that the defective design of the RnP was to blame because her infant son, A.B., had died from sleeping in it. The dangers of this inclined sleeper product were widely debated in this case.
It all started when A.B.’s mother, Plaintiff Ameena Brown, was gifted a secondhand Rock ‘n Play for A.B. During naptime and overnight sleep, Ameena would place A.B. supine in the RnP, which she kept in the living room.
On January 15, 2018, the day before A.B.’s death, there was nothing out of the ordinary about A.B.’s health or demeanor. At approximately 6:00 AM the next morning, Ameena awoke and went to check on A.B. A.B. was found dead in the Rock ‘n Play.
Erin Mannen’s investigation found, among other things, that inclined
sleepers can cause infants to roll from their back to their stomach or side and that once the infant is in this compromised position, the infant is at a heightened risk of suffocation. Defendants asserted that Mannen “ignored” studies commissioned by Fisher-Price that reached results contrary to her own and moved to exclude Mannen’s opinions.
Biomechanical Engineering Expert Witness
Erin Mannen is a biomechanical engineer who specializes in infant biomechanics and is the Director of the Boise Applied Biomechanics of Infants (BABI) Laboratory. She has published several peer-reviewed papers on the subject and won the American Society of Biomechanics Early Career Achievement Award for this work.
Discussion by the Court
It is noteworthy that A.B. suffered from several medical problems resulting from his premature birth, including hypertonicity. A.B. also suffered from developmental delays. Brown placed A.B., clothed and swaddled, on his back in the RnP. Sometime during the night, A.B. came to be on his side. When Brown awoke, she discovered A.B. “stiff.” Emergency services were unable to revive A.B.
Mannen’s report considered the effect inclined sleep products have on an infant’s ability to roll from their back, an infant’s ability to correct a compromised position after rolling, the rate at which an infant attempting to correct its position would fatigue, and the consequences those compromising positions would have on an infant’s breathing.
Mannen Qualifies As An Expert On Biomechanics
Mannen’s testimony would also show the use of an inclined sleeper makes it harder for an infant to correct a compromising position. Mannen’s report also touched on the topic of rebreathing. Defendants contended that: (1) Mannen did not qualify as a medical doctor and cannot give medical opinions; (2) Mannen failed to account for the specific conditions present in this case, thus preventing any of the findings of her studies from being applied to the instant set of facts; and (3) Mannen’s studies did not support her conclusion and did not utilize reliable methodology.
The Court found that her knowledge, skill, experience, training, and education meet the level of qualification required under Daubert. In other words, Defendants did not meaningfully contest Mannen’s qualifications as an expert on biomechanics.
The specific causation testimony that Defendants objected to concerned the following conclusions: (1) rebreathing and its impact; (2) the design of the RnP facilitated A.B. turning his head and coming into contact with the soft mesh siding of the RnP; (3) A.B. died from either positional asphyxiation or suffocation; and (4) the RnP caused A.B.’s death. Defendants argued that Mannen’s lack of medical expertise precluded her from opining on the topics of rebreathing and A.B.’s cause of death. Defendants further asserted a blanket objection to “any other specific causation opinion.” Plaintiffs contended that Mannen does not offer any medical opinions, and all of her opinions regarding specific causation are based on her expertise in biomechanics.
Mannen’s Causation Testimony Is Generally Admissible
Defendants argued Mannen’s opinion on rebreathing should be excluded because she does not qualify as a pulmonologist and improperly relied on the report of another expert, Michael D. Leshner.
The Court held that Mannen’s lack of qualification as pulmonologist does not necessarily preclude her from opining on rebreathing, as an expert may rely on the reports of other experts to help form the basis of their own opinion.
Her opinion, formed based on her analysis of Leshner’s data, states “in a side-lying or a 90-degree head turn situation, [ ] an infant would experience significantly increased CO2 inhalation simply due to the design of the product.”
Mannen synthesized that data generated by Leshner’s report; considered her peer-reviewed research, her inspection of the product, and her own expertise in biomechanics; and concluded that the environment created by placing an infant in the RnP creates “a dangerous CO2 rebreathing and/or suffocation scenario.”
Due to the deficiencies in that other Leshner’s methodology, the Court held that Mannen may not rely on Leshner’s report.
The Court struck Mannen’s conclusion that “in a side-lying or a 90-degree head turn situation, an infant would experience significantly increased CO2 inhalation simply due to the design of the product” because it was calculated with the data from Leshner’s unreliable methodology.
The Court concluded that Mannen’s other conclusions regarding whether an infant would be at risk for rebreathing in the RnP were based on her examination of an RnP, her peer-reviewed research, and her expertise as a biomechanical engineer. Accordingly, Mannen’s testimony regarding rebreathing that does not rely on Leshner’s methodology is admissible.
Mannen’s Studies Sufficiently Fit The Instant Facts and are Admissible
Mannen’s various studies examined infants and their muscle activity when placed at various inclines. Mannen studied healthy infants wearing only a diaper.
On the night of his death, A.B.’s limbs were restricted by a swaddle and layers of clothing. A.B. also suffered from hypertonicity, a condition of excessive muscle tone that may limit an infant’s range of motion.
Defendants argued that these variations between the facts surrounding A.B.’s death and Mannen’s studies prevented Mannen’s opinion from possessing the requisite fit to be admissible.
Mannen concedes she did not study infants who were clothed or swaddled, or any infants suffering from hypertonicity. Nevertheless, her studies and report explain how an infant previously unable to roll on his own may have been able to roll because of the incline present in the RnP. Further, her report explains how once A.B. rolled to his side, he may have been unable to reposition and would have struggled to breathe correctly. The Court held that these explanations are relevant to the ultimate issue in this case—how the RnP’s design may have contributed to A.B.’s death.
Defendants posited that Mannen, relied on tests that did not involve persons with the victim’s characteristics. However, the Court found that Mannen had a basis on which to assert that her conclusions regarding the risk of rolling for infants not suffering from hypertonicity could be applied to A.B. Mannen, provides an “ordinary infant” standard and applies that standard to an infant less susceptible to injury; thus, there is no additional susceptibility to injury that would invalidate her conclusions as applied to A.B.
Mannen’s Studies Employed Reliable Methodology
Defendants argued Mannen’s “easier-to-roll” hypothesis is unsupported by the studies she cites.
As to Mannen’s conclusion that a side-facing infant would come into contact with the side of the RnP, leading to an increased risk of suffocation, Defendants argued that Mannen’s demonstration using a soccer ball in place of an infant “is not based on any recognized methodology for examining potential respiratory compromises.”
Mannen’s studies—the 2019 Consumer Product Safety Commission study (the “CPSC study”) and the studies identified as “Wang 2020” and “Wang 2021″—examined the effects of sleep surfaces on an infant’s muscle activity to determine “if the design of inclined sleep products impacted suffocation risk from a movement and body position perspective.”
While conducting the CPSC study, Mannen studied ten infants placed on sleeping surfaces with increasing levels of incline. Mannen and her team monitored body position and muscle activity. Mannen subsequently conducted a similar study involving 15 infants, and published those results in peer-reviewed journals as the Wang 2020 and Wang 2021 studies.
Those studies found that infants placed in inclined sleepers experience different muscle activity and body position compared to infants on flat surfaces. Mannen opined that those differences make it easier for an infant to roll from supine to prone—a roll that necessitates the infant being on his side if only for a brief moment—which places the infant at greater risk of maneuvering into a compromised position.
The studies were not intended to measure the frequency infants rolled when placed in inclined sleepers, but rather the inclined sleeper’s biomechanical effect on an infant’s ability to roll.
Held
The Court found that Mannen explained her methodology; addressed what each finding means generally and in relation to A.B.’s case; considered potential errors within the studies; and subjected both the Wang 2020 and Wang 2021 studies to peer review.
Moreover, Defendants appeared to misinterpret Mannen’s use of a soccer ball in her opinion.
Defendants contend “that test, however, which involved manipulating a soccer ball by hand in a [RnP], is not based on any recognized methodology for examining potential respiratory compromises, and the test appears to have used a [RnP] model with an additional pad…” Mannen, however, did not perform a test with a soccer ball. Rather, she used the soccer ball in a series of pictures to demonstrate how something approximately the size of an infant’s head would be positioned after a 90-degree turn.
Mannen’s use of a soccer ball as a stand-in for an infant’s head appeared reasonable to the Court. As the soccer ball’s utilization was illustrative rather than substantive, that illustration is admissible.
The Court concluded that many of Defendants’ challenges relate to credibility and may be dealt with during cross-examination of Mannen. It was decided that Mannen may testify regarding rebreathing only to the extent that she relies on peer-reviewed studies or her own expertise; accordingly, Mannen’s rebreathing testimony may not touch on Leshner’s Report or any conclusions reliant on his methodology.
Key Takeaway:
Mannen utilized her expertise in biomechanics to opine: (1) how the RnP design allowed A.B. to turn onto his side; (2) how the RnP design made it more difficult for A.B. to correct his position once on his side; (3) the risk of rebreathing and suffocation created by the RnP; and (4) the increased fatigue caused by an infant unable to correct his position. None of those opinions offer a medical opinion. All those opinions are either the direct product of Mannen’s expertise, or her reasonable reliance on the reports of other experts. Thus, Mannen’s lack of medical expertise does not preclude her from offering those opinions.
Case Details:
| Case Caption: | Ameena Brown V. Fisher-Price, Inc. |
| Docket Number: | N20C-01-067 |
| Court: | Superior Court of Delaware, New Castle |
| Order Date: | December 20, 2024 |
