The Minnesota Supreme Court recently determined that a DWI or DUI* suspect does not have a right to counsel before making his or her decision about whether to submit to a blood or urine test pursuant to a warrant. Our last article explains that decision in further detail, including how it departs from longstanding history with regard to DUI testing in Minnesota.
*While there are some finer legal nuances between the terms Driving While Impaired (DWI) and Driving Under the Influence (DUI) under the law, DUI will be used in this article as a catchall for both terms because the distinctions are not pertinent to the topic of retrograde extrapolations.
What happens when a DUI suspect submits to testing, but that test is completed long after the person was driving their vehicle? After all, what can a test that is taken 2, 3, or 4 hours after a person was driving really say about the person’s blood alcohol concentration (BAC) or ability to drive a motor vehicle at the time they were actually driving?
That issue will be explored and explained in this article. The DWI and DUI attorneys at Lundgren & Johnson have extensive knowledge about retrograde extrapolations and have utilized that knowledge to obtain successful results for their clients.
Minnesota DUI Statutes Allow Testing Within Two Hours
The Minnesota legislature has taken this exact issue into consideration when fashioning Minnesota DUI laws. Minnesota Statute Section 169A.20, subdivision 1(5) criminalizes a person driving with an alcohol concentration of .08 or more at the time of driving, or as measured within two hours of the time of driving. Minnesota Statute Sections 169A.20, subdivisions 1a(5), 1b(5), and 1c(5), allow the same prosecutions for offenses in motorboats, snowmobiles, and off-road vehicles, respectively.
So if the police don’t obtain a blood, breath, or urine sample within two hours, the person can’t be charged with a DUI under those statutes, right? Wrong. This is a common misconception held by many motorists (and unfortunately some mistaken DUI defense attorneys, too). Prosecutors across Minnesota routinely rely upon the Minnesota Bureau of Criminal Apprehension to calculate “retrograde extrapolations” of a person’s BAC when the test is taken outside of the two hour statutory window. “Retrograde extrapolation” is a scientific term that basically means guessing someone’s alcohol concentration at an earlier point in time. The prosecutor will routinely ask a forensic scientist at the Minnesota Bureau of Criminal Apprehension to take the person’s BAC test result from outside of the two hour window, and estimate what it would have been at some point inside of the two hour window.
DUI Retrograde Extrapolations Are Vulnerable To Attack
Another common misconception, this one mostly by mistaken DUI defense attorneys, is that those retrograde extrapolation calculations are ironclad. They are not – and many are based on faulty science due to a lack of known variables required to perform the calculation. However, many of those calculations find their way into evidence, and DUI cases are allowed to proceed, because not all DUI defense attorneys understand the science and law related to retrograde extrapolations.
Before the science is addressed, we’ll cover some of the more common reasons why a DUI test is taken outside of the two hour window.
Common Scenarios That Lead To DUI Testing Outside Of Two Hours
Two hours is a long time, but many tests conducted in DUI cases are taken more than two hours after a DUI suspect was driving. A combination of the variables outlined below create situations where the police cannot obtain a test within two hours of a suspect’s driving:
- Time needed for the initial stop and investigation;
- Time needed for field sobriety testing and the preliminary breath test;
- Time needed to wait for a tow truck to secure the suspect’s vehicle if it is in a problematic location and a secondary officer is not available to respond;
- In cases where the suspect has already made it home or to another location, the time necessary to make contact with that person;
- The time necessary to transport the person to the police department, hospital, or other location where testing will take place;
- In cases of blood and urine tests, the time necessary to draft the search warrant application, contact a judge, and secure a search warrant;
- In cases of a breath test, various malfunctions the machine can encounter; and
- In cases of a breath test, the time necessary to complete the Minnesota Breath Test Advisory and the time it takes for the person to contact an attorney, if they so choose.
These are just a handful of examples. There are countless variables that can arise in the field that will delay testing beyond the two hour statutory window.
So if your test was taken outside of two hours from when you were driving, how can an experienced lawyer attack the retrograde extrapolation that the prosecutor will undoubtedly obtain from the Minnesota Bureau of Criminal Apprehension?
Retrograde Extrapolations – Too Many Unknown Variables
Retrograde extrapolation is the concept of estimating the alcohol concentration at a time prior to the completion of the alcohol concentration test. Determining or estimating a person’s peak blood alcohol concentration is critical for this estimation because if you extrapolate into a person’s absorption phase of alcohol (the time period after drinking while the person’s BAC is still rising), the extrapolation will overestimate their true alcohol concentration. There is no standard, uniform time period for when a person will reach their peak blood alcohol concentration. The time to reach peak blood alcohol concentration varies significantly across the population as a whole, and varies even in specific individuals depending on the circumstances of the specific drinking episode.
The scientific literature on this topic agrees that when the only information available is the time from cessation of drinking and a single blood, breath, or urine analysis, there is no forensically valid forward or backward extrapolation. For an extrapolation to be valid, important variables need to be known such as a person’s sex, height, weight, time of the person’s first drink, time of the person’s last drink, pattern of drinking, what kind of alcoholic beverages were consumed, and whether there is food in the stomach.
Unknown Variables, Unreliable Results
As you may suspect, the police don’t often gather information about all of those variables, nor do they even try. They simply have the person’s measured BAC, and the time of the person’s arrest. Does the Minnesota Bureau of Criminal Apprehension decline to perform the calculation due to insufficient information in those circumstances? No.
Instead, the Bureau of Criminal Apprehension uses uniform, standard numbers, which in and of themselves are estimates or guesses based on general population data. In turn, they use those estimates to perform the retrograde extrapolation, another estimation. See the problem here? Minnesota courts have, and they’ve addressed this specific issue on a number of occasions. Two of the primary cases for this issue will be discussed below.
The first published case to determine the admissibility of expert testimony regarding retrograde extrapolation was State v. Jensen. The court determined that expert testimony regarding retrograde extrapolation was admissible in that case when the experts had information about the height, weight, gender, amount and type of food eaten, the type of alcohol consumed, when the defendant drank his last beer, the time between the accident and testing, and that no alcohol was consumed after the accident. Importantly, the Jensen court acknowledged that the estimated range of the retrograde extrapolation calculated for that case (.181 to .31) was well above the legal threshold of .10, as opposed to being near the threshold. Both of the experts in Jensen acknowledged that the, “scientific community generally accepts the basic principles of retrograde extrapolation, but that retrograde extrapolation is unreliable when an expert has insufficient information about variables.” In a footnote, the Jensen court opined that challenges to expert testimony on retrograde extrapolation would likely go to the weight, rather than the admissibility, of such evidence.
However, the Minnesota Supreme Court subsequently considered the admissibility of retrograde extrapolation testimony in State v. Wolf. Wolf was a case where the experts did not have as much information about the defendant’s drinking episode and its associated variables as was known in Jensen. In affirming the district court’s decision to exclude expert witness testimony regarding retrograde extrapolation in that matter, the Minnesota Supreme Court explained:
The record, as stipulated to by both parties at trial, does not contain all the information necessary to conduct retrograde blood alcohol level calculations. The record does not contain such basic information as when Wolf last consumed alcoholic beverages, the amount and type of alcohol consumed, or even his accurate height and weight at the time of arrest. In the absence of an offer of proof and on the stipulated record, we cannot conclude that the district court’s ruling was an abuse of its discretion concerning the admissibility of evidence.
To be sure, the variables outlined above are not arbitrary. The variables have an impact on when a person’s body will reach the point of substantial absorption for the alcohol he or she consumed. A reasonable calculation for substantial absorption is critical because that identifies when the person reaches their peak alcohol concentration. If a scientist incorrectly extrapolates back into the absorption phase, then the estimated alcohol concentration will be higher than the reported value when in reality it would have been lower than the reported value.
What can be done about a DUI case that is based on an unreliable retrograde extrapolation?
DUI Defenses To Unreliable Retrograde Extrapolation
Evidentiary rulings, including the admission of expert testimony, are within the broad discretion of the district court. Expert testimony is admissible at trial only if (1) it assists the trier of fact, (2) it has a reasonable basis, (3) it is relevant, and (4) its probative value outweighs its potential for unfair prejudice.
Speculative assumptions on important variables, and lack of consideration or information about other important variables, renders any testimony irrelevant, unreasonable, and unhelpful. Furthermore, when that “evidence” comes from a scientist cloaked with the authority of Minnesota’s preeminent forensic authority, the Bureau of Criminal Apprehension, that creates a grave potential for unfair prejudice to the DUI defendant.
In the appropriate cases, an experienced DUI lawyer will understand how to explain why a retrograde extrapolation does not meet the criterion necessary for its admission into evidence. The DUI lawyer can ask the judge to prohibit the prosecutor from using the retrograde extrapolation. When successful, the result is dismissal of charges, or seriously hindering the prosecutor’s ability to further prosecute the case.
If You’re Charged With DUI, Contact Lundgren & Johnson Today
The experienced DUI attorneys at Lundgren & Johnson are eager to defend your DUI case, whether it is based on an unreliable retrograde extrapolation, or any of the other number of potential issues that can arise. Give Adam Johnson or David Lundgren a call today at 612-767-9643. They look forward to speaking with you.