---
title: "Human Factors Expert’s Opinion on Driver Inattentiveness Excluded"
meta:
  "og:description": "A jury does not require expert opinion to understand that distracted individuals can make errors"
  "og:title": "Human Factors Expert’s Opinion on Driver Inattentiveness Excluded"
  author: "Expert Witness Profiler"
  description: "A jury does not require expert opinion to understand that distracted individuals can make errors"
---

# Human Factors Expert’s Opinion on Driver Inattentiveness Excluded

Posted on June 20, 2025 by Expert Witness Profiler

This case arises out of an alleged design defect and failure to warn regarding a 2017 Toyota Tacoma. Lee Griffin was the primary driver of a 2017 Toyota Tacoma. After Griffin died due to accidental carbon monoxide poisoning from an automobile inadvertently continuing to run in the garage, Caroline Griffin filed suit individually and as executor of Lee Griffin’s estate.

The Plaintiff filed a motion to exclude the entire testimony of [Randall Tackett](https://expertwitnessprofiler.com/expert-witness/Randall-Tackett/1514633) and [Angela McGrath](https://expertwitnessprofiler.com/expert-witness/Angela-McGrath/1565130) as well as part of the testimony of [Nathan Dorris](https://expertwitnessprofiler.com/expert-witness/Nathan-Dorris/1514264) and [Harry Pearce II](https://expertwitnessprofiler.com/expert-witness/Harry-Pearce/1565131).

## **Toxicology Expert Witness**

Dr. [Randall Tackett](https://expertwitnessprofiler.com/expert-witness/Randall-Tackett/1514633) received his BS from Jacksonville University in 1975. He then received an MS degree in pharmacology and toxicology from Auburn University in 1977 and his Ph.D. in pharmacology and toxicology from the University of Georgia in 1979. Following a two-year postdoctoral fellowship at the Medical University of South Carolina, he returned to the University of Georgia as an assistant professor in the Department of Pharmacology and Toxicology.

He later served as a Professor and Associate Department Head in the Department of Clinical and Administrative Pharmacy at the University of Georgia College of Pharmacy.

[Get the full story on challenges to Randall Tackett’s expert opinions and testimony with an in-depth Challenge Study.](https://expertwitnessprofiler.com/order/add?eId=1514633&amp;pId=3)

## **Statistics Expert Witness**

[Angela A. McGrath](https://expertwitnessprofiler.com/expert-witness/Angela-McGrath/1565130) has a Bachelor of Science in Statistics, a Master of Arts in Applied Statistics, 27 years of experience in consulting, and experience teaching statistics.

She is the Principal Consultant and Director of Automotive Research at Cirque Analytics, an economic, statistical, and financial consulting company headquartered in Jackson Hole, WY. She has developed extensive experience in formulating, conducting, and directing statistical and other quantitative analyses.

[Want to know more about the challenges Angela McGrath has faced? Get the full details with our Challenge Study report.](https://expertwitnessprofiler.com/order/add?eId=1565130&amp;pId=3)

## **Automotive Engineering Expert Witness**

[Harry Pearce](https://expertwitnessprofiler.com/expert-witness/Harry-Pearce/1565131) has over 24 years of expertise in the field of structural crashworthiness. He gained industry experience with nine years at General Motors, serving as the Lead Structural Design Engineer for multiple vehicles.

With his knowledge and experience with vehicle sealing, Pearce has addressed claims of Carbon Monoxide (CO) intrusion. He has performed Electro Magnetic Interference (EMI) testing in anechoic chambers and Brake Override System (BOS) testing at Exponent’s Test and Engineering Center.

[Discover more cases with Harry Pearce as an expert witness by ordering his comprehensive Expert Witness Profile report.](https://expertwitnessprofiler.com/order/add?eId=1565131&amp;pId=3)

## **Human Factors Expert Witness**

[Nathan Todd Dorris](https://expertwitnessprofiler.com/expert-witness/Nathan-Dorris/1514264) is a human factors specialist with extensive experience in product safety and the evaluation of instructions, warnings and other safety communications for a broad range of products and industries.

[Gain a comprehensive understanding of Nathan Dorris’ qualifications and casework history with his Expert Witness Profile report.](https://expertwitnessprofiler.com/order/add?eId=1514264&amp;pId=3)

## **Discussion by the Court**

### **A. Randall Tackett**

Randall Tackett stated two opinions in his expert report:

1. Griffin consuming 1.2 standard drinks within the hour before death is inconsistent with the evidence described above. Rather, the timeline of events is consistent with Lee Griffin ingesting higher amounts of alcohol earlier on July 4, 2022, which his body would have metabolized from the time he ingested the alcohol until his death.

2. It is more likely than not that on the evening of July 4, 2022 Griffin’s blood alcohol concentration was at a level that could have affected his reaction time, hearing, judgment, memory, reasoning and ability to detect danger including his ability to turn off his Toyota Tacoma and/or recognize that it was still running in the garage.

#### **Motion to Exclude**

In this case, Tackett attempted to estimate the decedent’s blood alcohol content (BAC) at various times before death using a method known as retrograde extrapolation. The Plaintiff did not dispute the scientific validity of this technique in general. Instead, she argued that Tackett lacked the necessary factual basis to apply it reliably in this case.

Specifically, the Plaintiff pointed out several critical unknowns: the exact time of death, the time the vehicle was parked, and any concrete details about when, what, or how much alcohol the decedent consumed. The Defendants contended that these gaps in information should affect how much weight the jury gives Tackett’s testimony, not whether it should be allowed at all. The Court disagreed.

The main issue, according to the Court, was the absence of reliable timing data. Without knowing when key events occurred, it was unclear how far back Tackett should extrapolate. His estimates ranged from one to two hours before death to as far as 14–15 hours earlier. As a result, his BAC estimates varied widely—from 0.046 to 0.297—depending on assumptions about timing and the decedent’s metabolism rate. Notably, there was also no evidence that the decedent had consumed any alcohol before parking the car, further undermining the reliability of Tackett’s conclusions.

### **Angela McGrath**

The Defendants have proffered Angela McGrath as an expert witness to testify about the following opinions:

a. [The United States Consumer Product Safety Commission (“CPSC”)] death certificate data shows that vehicles with and without keyless ignition have inadvertently been left running in enclosed spaces.

b. Available CPSC death certificate data does not show a consistently increasing trend of accidental carbon monoxide poisoning from passenger vehicle exhaust in enclosed spaces.

c. The proportion of combustion engine vehicles on the road with keyless ignition is increasing over time, however, even by 2021, the majority of vehicles still have conventional keys.

d. While number of registered vehicles with keyless ignition and without [automatic engine time-out (“ETO”)] has increased steeply since 2011, the rates of accidental carbon monoxide poisoning from passenger vehicle exhaust in enclosed spaces has exhibited no corresponding, consistently increasing trend.

#### **Motion to Exclude**

The Plaintiff argued that McGrath’s opinions were unreliable because the CPSC database she relied on did not distinguish between carbon monoxide poisoning deaths caused by vehicles with keyless ignition systems and those with traditional mechanical ignitions. As a result, the Plaintiff contended that no meaningful statistical analysis could be done to compare the risks associated with each type of ignition system.

In response, the Defendants claimed the Plaintiff had misrepresented McGrath’s testimony. They asserted that McGrath was not attempting to directly compare the risks of carbon monoxide deaths between mechanical and keyless ignition systems. However, this argument fell short.

The Court noted that McGrath’s analysis implicitly relied on such a comparison. Her underlying logic was that if keyless ignition systems were more dangerous, the overall number of accidental carbon monoxide deaths would have increased after their introduction. Because the death rate did not rise, she inferred there was no added risk. Therefore, despite the Defendants’ assertions, McGrath’s analysis did, in fact, depend on comparing the two types of ignition systems—making the Defendants’ denial unconvincing.

Moreover, the Defendants’ argument rested on the assumption that, absent a defect, accidental carbon monoxide deaths would have remained constant from 2011-2021. The Court found this assumption questionable. Public awareness campaigns, increased usage of carbon monoxide detectors, or other safety measures could have contributed to a decline in deaths over time—independent of any defect. McGrath’s analysis failed to account for such alternative explanations.

Ultimately, the Court held that McGrath’s testimony offered nothing more than a basic correlation and lacked consideration of other plausible factors. As such, her statistical analysis could not be reliably used to show the absence of a defect.

### **Nathan Dorris**

The Plaintiff sought to exclude four categories of opinions that Dorris asserted: (1) that the Tacoma’s warnings were sufficient, (2) that drivers lose focus while using their vehicles, (3) that the Plaintiff and decedent should have had carbon monoxide detectors in their home, and (4) that the Tacoma was not defective because it complied with regulatory and voluntary standards.

#### **Inattentive Drivers**

The Plaintiff sought to exclude Dorris’ opinions regarding how driver inattentiveness could lead individuals to leave their engines running and fail to respond to alerts or other feedback.

In response, the Defendants argued that _“_ Dorris’ discussion of driver distraction is just one component of the opinions he expresses in this case and is background to his primary opinions specific to the 2017 Toyota Tacoma’s Smart Key System and the subject incident_.”_

The statements in question included: _“_ [d]rivers that are distracted or inattentive (for whatever reason) can inadvertently leave their vehicle’s engine running, regardless of the type of ignition system employed,” and “[n]ot only can inattention result in execution errors and omitted actions, but it may cause individuals not to respond to alerts or other feedback_.”_

Dorris was not particularly clear about whether these statements—or others like them—were independent expert opinions or merely facts supporting other opinions. Even the Defendants appeared uncertain. On one hand, they described these statements as _“_ background to his primary opinions_,”_ but on the other, they defended his ability to offer them as standalone opinions.

While Dorris may not opine directly that a driver’s inattentiveness causes errors, the Court held that if that fact properly supported a valid expert opinion offered by Dorris, he was permitted to rely on it.

#### **Sufficiency of the Warning**

Dorris opined that the warning provided by Toyota are “reasonable and appropriate.” The Plaintiff asserted that that opinion is unhelpful because it does not offer any analysis outside of what the jury can do itself.

Whether a warning is legally sufficient depends upon the language used and the impression that such language is calculated to make upon the mind of the average user of the product. The Court held that the adequacy inquiry here takes the perspective of the user of the product. Therefore, the jury is fully capable of determining whether the adequacy of the warning(s) at issue here without the help of an expert.

#### **Carbon Monoxide Detectors**

The Plaintiff argued that _“_ Dorris attempted to opine that the Griffins should have equipped their home with carbon monoxide detectors_.”_

However, the only relevant statement on the page of Dorris’s report cited by the Plaintiff read:

_“_ In a publication dated 08/2020, the Georgia Department of Public Health explicitly discussed CO exposure can cause ‘sudden illness or death’; potential sources of CO exposure include automobile exhaust; to install CO detectors ‘in every room used for sleeping’; ‘DO NOT leave a motor vehicle running in an enclosed garage_._“

This statement appeared under the section titled _“_ Exhaust Fumes and CO Are Well Known Hazards_.”_ Aside from the quoted portion referencing carbon monoxide detectors, there was no other mention of detectors—either in that section or anywhere else in the report.

The Court did not view this as Dorris offering an opinion that the Plaintiff or the decedent should have installed carbon monoxide detectors in their home. Instead, the Court found that he was merely citing a source he relied upon to support his broader conclusion that _“_ Exhaust Fumes and CO Are Well Known Hazards_.”_

Importantly, the Plaintiff did not challenge Dorris’s qualifications to reach that conclusion, nor did they argue that the conclusion itself was unhelpful.

#### **Compliance with Relevant Standards**

The Plaintiff moved to bar Dorris from testifying that the Toyota Tacoma was not defective simply because it complied with minimum regulatory standards.

In response, the Defendants argued that the jury had a right to consider federal compliance when evaluating whether the vehicle’s design was reasonable. They further claimed that Dorris relied on compliance as just one of several factors in concluding the Tacoma was not defective. However, the Court sided with the Plaintiff.

Dorris had stated that the lack of an automatic engine shutoff did not make the Tacoma defective, in part because _”_at the time the subject vehicle was manufactured and sold (and even today), such a feature is not required by any regulation or voluntary standard_.”_ In other words, he based his opinion on the fact that the Tacoma complied with federal regulations.

The Court found this reasoning insufficient and ruled that it warranted exclusion. Accordingly, the Court held that Dorris would be precluded from opining that the Tacoma was in compliance with federal regulation.

### **Harry Pearce II**

The Plaintiff sought to exclude four of his opinions from testimony: (1) opinions going to intent, motive, or state of mind, (2) opinions about the source of the carbon monoxide, (3) opinions about the efficacy of carbon monoxide detectors would have had in this case, (4) opinions “parroting” Jeya Padmanaban.

#### **Intent, Motive, and State of Mind**

The Plaintiff argued that Pearce should not be allowed to testify about Toyota’s subjective state of mind.

On that point, the Plaintiff was correct—Pearce could not offer opinions about what the Defendants were thinking, such as _“_ Toyota did not want to [install auto shutoff] because of the concern of introducing a new risk of hot car deaths_.”_ Such statements improperly speculate on Toyota’s intent or motivations.

However, the Defendants were also partially correct. Pearce was permitted to rely on Toyota’s internal documents and employee testimony to form his expert opinions. He _“_ may testify as to whether information contained in Defendants’ internal documents indicated certain risks_.”_ The Court clarified that while Pearce could interpret the content of internal materials to identify risk indicators, he could not speculate on Toyota’s actual intent or decision-making process.

#### **Source of Carbon Monoxide**

The Plaintiff moved to exclude any opinion from Pearce regarding the source of the carbon monoxide that caused her and the decedent’s injuries.

When asked directly whether he had an opinion on the source of the carbon monoxide in this case, Pearce responded, _“_ I was not asked to do that so I do not have an opinion on that._“_

Despite this, the Defendants added a qualification. They stated that Pearce would not offer an opinion on the matter _“_ unless Plaintiff opens the door to this subject through her attorneys’ examination of Pearce or the testimony of other witnesses she presents at trial._“_

But as the Defendants were well aware, the Plaintiff had already retained an expert specifically to testify about the source of the carbon monoxide. And since causation is a central element of the Plaintiff’s claims, it was almost certain the Plaintiff would _“_open the door_“_ to this issue during trial.

That, however, did not give the Defendants license to question Pearce on a subject about which he had explicitly disclaimed any opinion. If the Defendants wished to challenge the Plaintiff’s expert on the source of the carbon monoxide, they should have retained their own rebuttal expert.

#### **Carbon Monoxide Detectors**

Pearce intended to opine that, “[w]ith multiple sources of CO in a home, the best protection from CO exposure is the installation of CO detectors in the home. Auto engine shut-off only protects from the one vehicle on which it is installed.”

The Plaintiff objected to this because it depended on two assumptions: (1) that any carbon monoxide detectors in the house would have worked and (2) that the Plaintiff and the decedent would have responded to the carbon monoxide detector if it did work.

However, the Court held that Pearce has extensive experience from which he could derive his opinion.

#### **Parroting**

The Plaintiff argued that any testimony by Pearce regarding a 2015 paper published by Jeya Padmanaban would be irrelevant and amount to inadmissible “parroting.”

In response, the Defendants clarified that they did not intend to have Pearce testify about Padmanaban’s research. Instead, Pearce had included the study merely as general background material.

The Defendants confirmed that they would not raise the Padmanaban study at trial unless the Plaintiff opened the door to that line of testimony. Based on this clarification, the Court denied this portion of the Plaintiff’s motion to exclude.

## **Held**

- The Court granted the Plaintiff’s motion to exclude Randall Tackett’s testimony.

- The Court granted the Plaintiff’s motion to exclude Angela McGrath’s testimony.

- The Court granted in part and denied in part the Plaintiff’s motion to exclude Nathan Dorris’ testimony.

- The Court granted in part and denied in part the Plaintiff’s motion to exclude Harry Pearce’s testimony.

## **Key Takeaways:**

1. An expert’s testimony is not relevant and may be excluded if it is directed to an issue that is well within the common sense understanding of jurors and requires no expert testimony.

1. Experts may not testify that a party was in compliance with a federal regulation. Whether someone has violated or is in compliance with the law is a legal conclusion.

1. Expert testimony about a party’s intent, motive, or state of mind is inadmissible.

## **Case Details:**

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