Two toxicology experts are battling over the use of retrograde extrapolation in the trial of a former EMT who is on trial for vehicular homicide.
On July 3, 2018, 37-year-old former EMT and Hamilton County reserve deputy Justin Whaley was driving the wrong way on Highway 111 in Tennessee. Whaley’s vehicle crashed into another car head-on. The crash claimed the life of James Brumlow, who was driving the other car.
The police and EMS arrived on the scene within minutes; however, Whaley’s blood draw was not conducted for four hours after the police arrived on the scene.
Investigators said that Whaley was driving in the early morning hours after a night of drinking with a friend. Whaley was arrested and charged with vehicular homicide, reckless driving, two counts of failure to yield, failure to maintain lane, speeding, failure to exercise due care, and driving under the influence.
The Extrapolation Controversy
Because the blood was taken from Whaley four hours after the incident, the state had to extrapolate the results of the test to determine what his blood alcohol level would have been at the time of the accident. Whaley’s defense attorney, Lee Davis, asked for the results of the blood draw to be suppressed, arguing that the extrapolation was unreliable.
Prosecutor Chris Post retained East Tennessee State University professor Kenneth Ferslew of the William L. Jenkins Forensic Center to explain why the blood draw results should be admitted.
Professor Ferslew explained that “the body begins breaking down and processing alcohol from the moment it enters the body, but that as a person drinks, the amount of alcohol being broken down is outpaced by the amount coming in. When people drink more, then that’s when their blood alcohol content goes up. But after alcohol is no longer consumed, then the blood alcohol level goes down in a linear fashion.”
Professor Ferslew testified that, based on the time that the blood was drawn, the Tennessee Bureau of Investigation was “99.73 percent confident by statistical analysis that blood [had] a 0.02 gram percent concentration in it.” Professor Ferslew told the judge that if the police had waited even 15 minutes longer to draw the blood, the results would have been unusable. However, Professor Ferslew testified that the blood taken from Whaley could appropriately be used to determine that he was intoxicated when the crash occurred.
Defense attorney Davis brought in his own toxicology expert to explain why extrapolating the blood draw results would be unreliable. Jimmie Valentine, Ph.D., holds a degree in medicinal chemistry from the University of Mississippi and served as a professor of pharmacology at the University of Arkansas College of Medicine for 19 years.
Dr. Valentine testified that “Using this retrograde extrapolation is just not very scientific at this juncture. It’s best used when you have multiple samples from different times, so you can be sure.” Dr. Valentine pointed out that in other states, two or three samples would be taken over the course of several hours.
Judge Steelman, who is presiding over the case, announced that he would take both experts’ testimony into consideration and would make a decision about what the jury will hear when the case goes to trial in September.