Has your Michigan defense attorney factored in the science behind retrograde extrapolation? This science can sink your case, or be your greatest asset. Extrapolate means to estimate or to guess at the value of something that is outside a known range.The whole theory of retrograde extrapolation is based upon guesswork. The science is guessing a BAC based off a past value. In order for this science to be meaningful, it is necessary to have a BAC measurement at two different points in time. By having two values, the expert can create a “trend line” or “grade” of the BAC. If you have only one BAC measurement, the expert must assume by the time the driver’s blood is sampled, the BAC has begun to decrease. |
Widmark is the father of retrograde extrapolation. His “r” factor is the basis of his science, which is represents how alcohol is distributed throughout the body. His created values based upon the testing of 20 men and 10 women. He determined the average “r” factor for a man is 0.68 with a range of 0.52 to 0.86 and the average for a woman is 0.55 with a range of 0.47 to 0.64. There is no way for the state’s expert to know the defendant’s exact “r” factor.
Widmark also factors in the known BAC, an assumed amount of alcohol consumed, the client’s body weight, the elapsed time and assumes an elimination rate of alcohol from the body.
Most state experts assume the client has an average rate of elimination between .15-18 g/L per hour, yet there are published studies showing eliminations rates between .08 and .35 g/L/h.
Fitzgerald and Hume concluded that the Widmark “r” factor and assumption of alcohol elimination rate can lead to significant errors, improper calculations and unfair treatment of drunk drivers.
A major problem with Widmark’s formule is that the BAC does not remain constant. Absoption is not instantaneous neither is distribution of alcohol in the body. As soon as alcohol is consumed, the process of elimination automatically begins.
Widmark’s test subjects were dosed with alcohol at fixed, constant and prescribed times to get his “r” factor number. That is a lot different than how alcohol is normally consumed in a social setting. Drinks are various sizes and strengths and unequally spaced out.
Absorption is the process of moving alcohol from outside the body into the bloodstream where it can be distributed throughout the body. As a small, completely water-soluble molecule, ethyl alcohol is readily absorbed into the mucous lining of the digestive tract. When it comes into contact with the digestive tract, alcohol is absorbed via simple diffusion into the mucous lining and then into the blood. The amount absorbed at any given site depends upon the surface area, the thickness of the lining and the blood supply. Unlike most other ingested substances, alcohol is not digested and can be absorbed unchanged directly through the stomach lining. Only about 20-25% of ingested alcohol is absorbed in this manner because the stomach has a relatively small surface area and limited blood supply. The remaining 75-80% of the alcohol is rapidly and efficiently absorbed when it leaves the stomach and enters the small intestine, which has a large surface area and rich blood supply
How absorption might be slowed down - Because alcohol is rapidly absorbed once it reaches the small intestine, anything that delays the stomach from emptying its contents into the small intestine will slow the rate of alcohol absorption. The most rapid absorption takes place when a 20% solution of alcohol is consumed on an empty stomach. Diluted drinks take somewhat longer to absorb. In concentrated drinks (greater than 40% by volume) alcohol acts as an irritant to the gastric lining and will be retained in the stomach until it can be diluted. Alcoholic beverages containing ingredients that require digestion, such as carbonated beverages, may also slow absorption somewhat.
Absorption may also be affected by emotional state, shock and medications that impact stomach function and the general condition of the gastrointestinal tract. The most important factor affecting absorption is the presence of food in the stomach concurrent with alcohol. Food requires digestion and any alcohol trapped in food particles will take longer to be absorbed. The extent of the effect depends on the amount and type of food. The delay in absorption causes a lower peak alcohol concentration that lasts longer compared to consumption on an empty stomach.
State experts assume a lot of things when calculating their result. They assume the defendant is eliminating alcohol at the same rate as the population average, and that they were fully absorbed at the time of the arrest. The only way to be sure that the individual is in the elimination phase is to have at least two BAC values separated by time. When there is only one test, there is no way to establish when the alcohol absorption plateau was reached. The longer the period of time between the test and the violation, the greater the likelihood of error in using retrograde extrapolation.
Fitzgerald and Hume conclude that a single chemical test for intoxication is too unreliable to be admitted into evidence if the time delay between the violation and the test is greater than thirty minutes. Unless there are two specimens, it is impossible to determine whether absorption or elimination is occurring.
The more information the expert has, the more reliable the retrograde will be. The following factors would make the calculation more reliable
What type of alcohol?
How much alcohol?
Concentration of alcohol?
Over what period of time?
How much does the defendant weigh?
History of alcohol use by defendant?
What did the defendant eat? Still food in stomach?
Two leading research scientists (Dr. Kurt Dubowski and Dr. A.W. Jones) on the subject of retrograde extrapolation have expressed reservations concerning the reliability and feasibility of this science for forensic purposes. Both of these scientists at some point taught the “Robert F. Borkenstein Course on Alcohol, Drugs and Highway Safety: Testing, Research and Litigation” which is taught at Indiana University. State experts attend this course to learn how to perform retrograde extrapolation.
Dr. Dubowski believes that it is nearly always impossible for the state to have enough information about the defendant to reliably preduct a previous blood alcohol content. He calls the science speculative and should be avoided in forensic practice. He says that if the science is attempted in the courtroom, the opinion must be so qualified by stated assumptions that the exercise becomes pointless. His reasons are the following:
An essential assumption with retrograde is that blood alcohol content will increase and decrease in a straight line, but this is not true for every person.
Alcohol elimination does not always neatly follow a smooth curve as the blood alcohol concentration moves up or down. Individual breath or blood levels are often subject to short-term fluctuations and other irregularities. Because of these fluctuations, the elimination of alcohol does not always follow the Widmark formula.
Alcohol is not always uniformly distributed between the cellular and noncellular components of blood and because of the relative frequency of blood-based abnormalities in the population. Because of this, extrapolation of a later alcohol test result to the time of the offense is always of uncertain validity and therefore forensically unacceptable.
The most important determination for an expert is when the defendant reached full absorption. This becomes the baseline from which a retrograde blood alcohol level can be determined. Most state experts will say full absorption has occurred after 60 to 90 minutes; Dr. Dubowski gives a range of full absorption between 14 and 138 minutes, and even longer for some people.
Dr. Jones believes for forensic purposes, an extrapolated BAC should be given within a range of value. And that in fairness to a criminal defense, the lowest value should be assigned. He says that retrograde extrapolation is based on assumption, because of the pharmacokinetic of ethanol in a given individual. He says that when calculating elimination rate, several values should be considered, and because of this calls retrograde extrapolation not forensically feasible and labels it as “dubious”. Alcohol consumed within 30-60 minutes of the offense has the most forensic relevance.
Cross-Examination of State’s Expert
The studies and writings of Dr. Dubowski and Dr. Jones should be used during cross-examination in order to demonstrate how much guess work is required to perform retrograde extrapolation.
The state expert will make a variety of assumptions in their calculations; if the assumptions were different, the conclusion would also be different. The expert is factoring in different assumptions opens up the possibility of a lower BAC.
- On cross, it may be possible to have the expert admit that he has previously not been allowed to testify about retrograde extrapolation, because the judge did not allow it.
- Have the expert agree that there are two schools of thought within the scientific community specifically Dr. Dubowski and Dr. Jones.
- Confront the expert with the opposing school of thought that this science is not forensically valid, and not appropriate in criminal matters
- Retrograde extrapolation is another way to say metabolism of alcohol – metabolism is based on three principles: absorption, distribution and elimination
- Get expert to agree that the rate at which somebody absorbs varies from person to person
- A person’s physiology can also impact on the way the person absorbs alcohol
- The amount of water in their entire body can have an impact on the way alcohol is absorbed
- Gender, Race, Height, Weight, Age all matter
- Lock expert into saying he does not know the manner in which or the rate at which the defendant absorbed alcohol
- Don’t know the manner in which or the rate at which alcohol was distributed in the defendant’s body
- The expert doesn’t know the elimination rate for the defendant – it is mere speculation
- Scientific literature has indicated that full absorption can occur between 14 minutes and 138 minutes, and longer for certain people
- It’s possible that the defendant’s last drink was still absorbing for 138 minutes and possibly longer, and that the defendant was still in the absorption phase well beyond the traffic stop in this case
- During absorption the blood alcohol level is rising
- You don’t know what the defendant’s absorption rate was
- But you might be able to have a better guess if you had two samples
- But in this case, you only have one, and one sample produces a less reliable guess at the elimination rate
- If a motorist consumed a substantial amount of alcohol right before the incident, this alcohol could take up to 138 minutes, almost 2 ½ hours to fully absorb
- So it's quite possible the driver's BAC was below 0.08 when operating, rose above that number for up to 2 1/2 hours then returned back under 0.08 when the driver was tested
Widmark also factors in the known BAC, an assumed amount of alcohol consumed, the client’s body weight, the elapsed time and assumes an elimination rate of alcohol from the body.
Most state experts assume the client has an average rate of elimination between .15-18 g/L per hour, yet there are published studies showing eliminations rates between .08 and .35 g/L/h.
Fitzgerald and Hume concluded that the Widmark “r” factor and assumption of alcohol elimination rate can lead to significant errors, improper calculations and unfair treatment of drunk drivers.
A major problem with Widmark’s formule is that the BAC does not remain constant. Absoption is not instantaneous neither is distribution of alcohol in the body. As soon as alcohol is consumed, the process of elimination automatically begins.
Widmark’s test subjects were dosed with alcohol at fixed, constant and prescribed times to get his “r” factor number. That is a lot different than how alcohol is normally consumed in a social setting. Drinks are various sizes and strengths and unequally spaced out.
Absorption is the process of moving alcohol from outside the body into the bloodstream where it can be distributed throughout the body. As a small, completely water-soluble molecule, ethyl alcohol is readily absorbed into the mucous lining of the digestive tract. When it comes into contact with the digestive tract, alcohol is absorbed via simple diffusion into the mucous lining and then into the blood. The amount absorbed at any given site depends upon the surface area, the thickness of the lining and the blood supply. Unlike most other ingested substances, alcohol is not digested and can be absorbed unchanged directly through the stomach lining. Only about 20-25% of ingested alcohol is absorbed in this manner because the stomach has a relatively small surface area and limited blood supply. The remaining 75-80% of the alcohol is rapidly and efficiently absorbed when it leaves the stomach and enters the small intestine, which has a large surface area and rich blood supply
How absorption might be slowed down - Because alcohol is rapidly absorbed once it reaches the small intestine, anything that delays the stomach from emptying its contents into the small intestine will slow the rate of alcohol absorption. The most rapid absorption takes place when a 20% solution of alcohol is consumed on an empty stomach. Diluted drinks take somewhat longer to absorb. In concentrated drinks (greater than 40% by volume) alcohol acts as an irritant to the gastric lining and will be retained in the stomach until it can be diluted. Alcoholic beverages containing ingredients that require digestion, such as carbonated beverages, may also slow absorption somewhat.
Absorption may also be affected by emotional state, shock and medications that impact stomach function and the general condition of the gastrointestinal tract. The most important factor affecting absorption is the presence of food in the stomach concurrent with alcohol. Food requires digestion and any alcohol trapped in food particles will take longer to be absorbed. The extent of the effect depends on the amount and type of food. The delay in absorption causes a lower peak alcohol concentration that lasts longer compared to consumption on an empty stomach.
State experts assume a lot of things when calculating their result. They assume the defendant is eliminating alcohol at the same rate as the population average, and that they were fully absorbed at the time of the arrest. The only way to be sure that the individual is in the elimination phase is to have at least two BAC values separated by time. When there is only one test, there is no way to establish when the alcohol absorption plateau was reached. The longer the period of time between the test and the violation, the greater the likelihood of error in using retrograde extrapolation.
Fitzgerald and Hume conclude that a single chemical test for intoxication is too unreliable to be admitted into evidence if the time delay between the violation and the test is greater than thirty minutes. Unless there are two specimens, it is impossible to determine whether absorption or elimination is occurring.
The more information the expert has, the more reliable the retrograde will be. The following factors would make the calculation more reliable
What type of alcohol?
How much alcohol?
Concentration of alcohol?
Over what period of time?
How much does the defendant weigh?
History of alcohol use by defendant?
What did the defendant eat? Still food in stomach?
Two leading research scientists (Dr. Kurt Dubowski and Dr. A.W. Jones) on the subject of retrograde extrapolation have expressed reservations concerning the reliability and feasibility of this science for forensic purposes. Both of these scientists at some point taught the “Robert F. Borkenstein Course on Alcohol, Drugs and Highway Safety: Testing, Research and Litigation” which is taught at Indiana University. State experts attend this course to learn how to perform retrograde extrapolation.
Dr. Dubowski believes that it is nearly always impossible for the state to have enough information about the defendant to reliably preduct a previous blood alcohol content. He calls the science speculative and should be avoided in forensic practice. He says that if the science is attempted in the courtroom, the opinion must be so qualified by stated assumptions that the exercise becomes pointless. His reasons are the following:
An essential assumption with retrograde is that blood alcohol content will increase and decrease in a straight line, but this is not true for every person.
Alcohol elimination does not always neatly follow a smooth curve as the blood alcohol concentration moves up or down. Individual breath or blood levels are often subject to short-term fluctuations and other irregularities. Because of these fluctuations, the elimination of alcohol does not always follow the Widmark formula.
Alcohol is not always uniformly distributed between the cellular and noncellular components of blood and because of the relative frequency of blood-based abnormalities in the population. Because of this, extrapolation of a later alcohol test result to the time of the offense is always of uncertain validity and therefore forensically unacceptable.
The most important determination for an expert is when the defendant reached full absorption. This becomes the baseline from which a retrograde blood alcohol level can be determined. Most state experts will say full absorption has occurred after 60 to 90 minutes; Dr. Dubowski gives a range of full absorption between 14 and 138 minutes, and even longer for some people.
Dr. Jones believes for forensic purposes, an extrapolated BAC should be given within a range of value. And that in fairness to a criminal defense, the lowest value should be assigned. He says that retrograde extrapolation is based on assumption, because of the pharmacokinetic of ethanol in a given individual. He says that when calculating elimination rate, several values should be considered, and because of this calls retrograde extrapolation not forensically feasible and labels it as “dubious”. Alcohol consumed within 30-60 minutes of the offense has the most forensic relevance.
Cross-Examination of State’s Expert
The studies and writings of Dr. Dubowski and Dr. Jones should be used during cross-examination in order to demonstrate how much guess work is required to perform retrograde extrapolation.
The state expert will make a variety of assumptions in their calculations; if the assumptions were different, the conclusion would also be different. The expert is factoring in different assumptions opens up the possibility of a lower BAC.
- On cross, it may be possible to have the expert admit that he has previously not been allowed to testify about retrograde extrapolation, because the judge did not allow it.
- Have the expert agree that there are two schools of thought within the scientific community specifically Dr. Dubowski and Dr. Jones.
- Confront the expert with the opposing school of thought that this science is not forensically valid, and not appropriate in criminal matters
- Retrograde extrapolation is another way to say metabolism of alcohol – metabolism is based on three principles: absorption, distribution and elimination
- Get expert to agree that the rate at which somebody absorbs varies from person to person
- A person’s physiology can also impact on the way the person absorbs alcohol
- The amount of water in their entire body can have an impact on the way alcohol is absorbed
- Gender, Race, Height, Weight, Age all matter
- Lock expert into saying he does not know the manner in which or the rate at which the defendant absorbed alcohol
- Don’t know the manner in which or the rate at which alcohol was distributed in the defendant’s body
- The expert doesn’t know the elimination rate for the defendant – it is mere speculation
- Scientific literature has indicated that full absorption can occur between 14 minutes and 138 minutes, and longer for certain people
- It’s possible that the defendant’s last drink was still absorbing for 138 minutes and possibly longer, and that the defendant was still in the absorption phase well beyond the traffic stop in this case
- During absorption the blood alcohol level is rising
- You don’t know what the defendant’s absorption rate was
- But you might be able to have a better guess if you had two samples
- But in this case, you only have one, and one sample produces a less reliable guess at the elimination rate
- If a motorist consumed a substantial amount of alcohol right before the incident, this alcohol could take up to 138 minutes, almost 2 ½ hours to fully absorb
- So it's quite possible the driver's BAC was below 0.08 when operating, rose above that number for up to 2 1/2 hours then returned back under 0.08 when the driver was tested