The Charlotte Observer reports that a driver was charged yesterday in an accident which occurred Saturday night and resulted in the death of a moped rider. Shortly after 8:00 p.m. on Saturday night, a man was riding his moped on South Boulevard. He stopped his moped, while waiting to turn into a shopping center. While he was stopped, another driver came up behind him, failed to stop and rear-ended the moped. As a result of the collision, the moped driver was pushed out into a lane of oncoming traffic, where he was struck and killed by a third vehicle. The driver who rear-ended the moped driver fled the scene of the accident. The driver of the third vehicle remained at the scene and took note of the other driver’s car and tag number. The driver who fled the scene was later found at the address to which the car was registered. He was subsequently charged with driving while impaired, felony hit-and-run, and felony death by vehicle. The crash is still being investigated by police.
It is unclear from the article exactly how much time elapsed between the accident and the police’s encounter with the driver who was later charged. Typically when a person is charged with DWI, they submit to a breath or blood test soon after they have been driving so that the test indicates their blood alcohol content (BAC) at the time of their driving. However, sometimes enough time elapses between the accident and the breath tests so that at the time of the defendant’s test the BAC is below 0.08, but at the time of the accident the defendant’s BAC would have been above. Alternatively, a defendant might argue that although he was impaired when the police found him, he was not impaired at the time of the accident because he consumed alcohol after he arrived at home. In these types of situations, the State will sometimes introduce the testimony of an expert in retrograde extrapolation.
The North Carolina Supreme Court has described retrograde extrapolation as
a mathematical analysis in which a known blood alcohol test result is used to determine what an individual's blood alcohol level would have been at a specified earlier time. The analysis determines the prior blood alcohol level on the bases of (1) the time elapsed between the occurrence of the specified earlier event (e.g., a vehicle crash) and the known blood test, and (2) the rate of elimination of alcohol from the subject's blood during the time between the event and the test.
State v. Cook (2008)
If an expert has two BAC results from tests submitted to by the defendant sufficiently far enough apart, he can determine the defendant’s specific rate of elimination of alcohol. Typically, however, a testifying expert must use the average elimination rate of alcohol in his retrograde extrapolation because there are not two separate tests from the defendant spaced sufficiently far enough apart. Where the average elimination rate of alcohol is used in the expert’s retrograde extrapolation, courts have determined that this testimony can be admissible, but the possibility of a defendant’s individual elimination rate being different than the average rate goes to the weight of the testimony.
Let’s take the situation where enough time has elapsed after an accident that the defendant’s BAC is not at least 0.08. This is similar to the 2004 North Carolina Court of Appeals case, State v. Taylor. In Taylor, the defendant was involved in an accident around 1:00 pm. However, the defendant did not take his first breath test until 3:18 pm, at which time his BAC was 0.05. The State’s expert performed a retrograde extrapolation using an average alcohol elimination rate and determined that the defendant’s BAC at the time of the accident was 0.08. The court of appeals permitted the expert’s testimony on retrograde extrapolation using the average rate of elimination, in part because of prior case law which held retrograde extrapolation to be sufficiently reliable and in part because the retrograde extrapolation used a conservative elimination rate.
Now let’s consider the situation where a defendant argues that although his BAC is over the limit at the time of his encounter with the police, he was not impaired at the time of the earlier accident because he consumed alcohol after he arrived at home. This situation is similar to the 2011 court of appeals case, State v. Green. In Green, the defendant was involved in a hit-and-run accident shortly after 8:00 p.m. The police found him at his house a little after 9:30 p.m., at which time they noticed signs of impairment. The defendant was subsequently arrested for DWI, and a breath test administered at around 11:30 p.m. indicated a BAC of 0.19. The defendant argued that he consumed five glasses of wine after the accident at home.
The retrograde extrapolation expert testified that if the defendant had had nothing to drink after the accident, then the defendant’s BAC would have been 0.24 at the time of the accident. If the defendant had had one glass of wine after the accident, then the defendant’s BAC would have been 0.23 at the time of the accident. And if the defendant had had five glasses of wine after the accident, then the defendant’s BAC would have been 0.19 at the time of the accident. The expert noted that if the defendant had nothing to drink before the time of the accident, he would have had to consume 88 ounces of wine after driving to register a BAC of 0.19 at the time of the breath test. To make these determinations, the expert made several assumptions, including an assumption that the defendant drank 5 ounce glasses of wine containing 12% alcohol. The court permitted this testimony, noting the expert’s use of established techniques and professional background in the field.
If you have been charged with impaired driving, contact an attorney at Rosensteel Fleishman, PLLC (704) 714-1450, to discuss your options.