If this opinion indicates that it is “FOR PUBLICATION,” it is subject to 

revision until final publication in the Michigan Appeals Reports.

-1-

S T A T E O F M I C H I G A N

C O U R T O F A P P E A L S

PEOPLE OF THE STATE OF MICHIGAN,

Plaintiff-Appellee,

FOR PUBLICATION

November 10, 2022

v No. 357976

Ottawa Circuit Court

CARA CHRISTINE BOWDEN, LC No. 21-044535-AR

Defendant-Appellant.

Before: BORRELLO, P.J., and M. J. KELLY and REDFORD, JJ.

REDFORD, J. (dissenting)

From the majority opinion I respectfully dissent. I conclude that the circuit court correctly

affirmed the district court’s order qualifying Deputy Schaller as an expert Drug Recognition 

Evaluator (DRE) permitted to provide an opinion whether defendant operated her vehicle under 

the influence of marijuana to a degree that rendered her unsafe to drive. Defendant argues that 

Deputy Schaller should be precluded from testifying regarding her impairment because the DRE 

protocols do not permit detection of impairment with absolute scientific certainty. The majority 

agrees that his testimony should be precluded because the studies on which the prosecution relied 

only validated the DRE protocol’s accuracy in determining the presence of a substance in a 

subject’s blood but did not validate the DRE protocol for determining a subject’s degree of 

impairment. I disagree because evidence established that Deputy Schaller can reliably use the 

DRE protocol as an investigative tool among others to detect a person’s impairment and inability

to safely drive a motor vehicle because of marijuana use.

I. FACTUAL BACKGROUND

Deputy Schaller testified that he worked as a deputy safety officer of the Ottawa County 

Sheriff’s Office since 2004 primarily as a road patrol officer. He received training in standardized 

field sobriety tests (SFSTs) at the police academy, later became Advanced Roadside Impaired 

Driving Enforcement (ARIDE) certified, and became certified as a DRE after 80 hours of 

classroom work involving instruction in medical conditions, observable signs of drug impairment 

from different drugs, followed by fieldwork in which he performed tests on subjects and a final 

examination. He testified that he did 12 DRE evaluations during his training and 4 additional
-2-

evaluations during 2019, 45 evaluations in 2020, and had done 3 so far in 2021. He entered his 

evaluations into the National Highway Traffic Safety Administration’s (NHTSA) data tracking 

website which verified his evaluations as 97% accurate.

Following defendant’s arrest, Deputy Schaller conducted on defendant the 12-step DRE 

protocol. Deputy Schaller testified that the DRE protocol aids in determining the category of drug 

of which the suspect might be under the influence. He explained that the modified Romberg test 

enables the evaluation of the suspect’s ability to follow instructions, divide attention to perform 

multiple tasks not unlike that experienced in driving a motor vehicle, and the detection of

impairment and other observable physical traits indicative of possible impairment. During the 

walk-and-turn and one-leg stand tests, he monitors each aspect of a suspect’s performance 

including ability to listen to and exactly follow instructions, and perform the steps of each test 

without interruption, miscue, or need to balance, pause, or stop. The finger-to-nose test, another 

divided attention test, tests whether the suspect can follow instructions and do multiple tasks by 

having the suspect touch alternately the tip of the nose with a fingertip of each hand in the sequence 

the officer directs. During the Divided Attention Psychophysical Tests administration, Deputy 

Schaller also looks for observable clues and general indicators, among other things, body tremors, 

eyelid tremors, jerky movements, imbalance, and abnormal time perception.

After conducting the DRE protocol with defendant following her arrest, Deputy Schaller 

concluded, based upon the totality of all the information obtained in the investigation, that 

defendant was under the influence of and impaired by marijuana, making her unable to safely 

operate a motor vehicle. The Ottawa County Sheriff’s Office charged defendant with one count 

of operating while intoxicated in violation of MCL 257.625(1). Defendant’s toxicology lab test 

later confirmed that her blood contained delta-9 tetrahydrocannabinol (THC), the active ingredient

in marijuana.

Defendant moved in limine in the district court to preclude the introduction of evidence 

“related to any and all tests of defendant’s physiology, motor skills, comprehension, or 

coordination.” The prosecution moved for the district court to qualify Deputy Schaller as an expert 

in the field of Drug Evaluation and Classification and requested that Deputy Schaller be allowed 

to testify and render expert opinions as a DRE. The district court conducted a two-day evidentiary 

hearing on the parties’ competing motions at which Deputies White, Williams, and Schaller 

testified. Deputy White testified regarding the traffic stop, his detection of the presence of 

marijuana, his observance of defendant’s bloodshot eyes, and defendant’s performance during the 

SFSTs that he administered. Deputy Williams testified regarding defendant’s performance of the 

tests that he administered. Both deputies testified that they found deficiencies in defendant’s 

performance of some of the tests which caused them to believe that probable cause existed to arrest 

defendant for operating her vehicle while under the influence of a controlled substance in violation 

of MCL 257.625.

Deputy Schaller testified regarding the training he received to become DRE certified and 

his experience in performing DRE evaluations. Deputy Schaller testified at length regarding the 

DRE protocol evaluation process and the development of the DRE protocols in the late 1970s by 

the Los Angeles Police Department which later partnered with the NHTSA to perform validation 

studies in a laboratory setting and in the field with further development over the next 40 years. He 

explained that around 1984 the Johns Hopkins University conducted a lab-based validation double-
-3-

blind study with 80 volunteers who were administered drugs from specified categories in different 

doses and then evaluated using the DRE protocols to determine the success and error rate of using 

that method of detection of drug usage.1 The Johns Hopkins University study is referred to as the 

Bigelow Study. The study found a 90% success rate in using the DRE protocols for determining 

whether subjects were under the influence of drugs, and had a 98% success rate in determining if 

subjects were not impaired.

Deputy Schaller also testified regarding a 1986 field validation study conducted by the Los 

Angeles Police Department, referred to as the Compton Study,

2

in which 173 individuals who had 

been arrested for impaired-driving offenses other than alcohol were evaluated by DRE experts

using the DRE protocols. That study validated the DRE program’s reliability as a tool for use by 

law enforcement in investigating and determining drug impairment.

Deputy Schaller further testified regarding his observations of defendant during the traffic 

stop including that defendant had an odor of marijuana coming from both herself and from the 

vehicle in which she had been the sole occupant, she displayed bloodshot eyes, and that she told 

police officers that she had smoked marijuana 30 minutes before the traffic stop. He described in 

detail his observations of defendant’s performance of the SFSTs administered by Deputy White 

and the ARIDE tests administered by Deputy Williams. Deputy Schaller explained that, before he 

administered the DRE protocol, he felt that probable cause existed to believe that defendant 

operated her vehicle under the influence of marijuana. He testified that defendant’s performance 

of the tests under the DRE protocol confirmed that defendant operated her vehicle while impaired. 

He testified that, in his expert opinion, based upon the totality of the information obtained during 

the investigation, defendant was under the influence of marijuana and unable to safely operate a 

motor vehicle.

On cross-examination, Deputy Schaller conceded that persons could have a drug in their 

system and not be under the influence or impaired. He testified regarding the Bigelow Study and 

Compton Study and affirmed that he considered them accurate and valid studies. He described in 

detail the manner in which the Bigelow Study had been conducted under strict controls to permit 

accurate analysis of the drug impairment evaluation process. He acknowledged that he had some 

limitations as to knowledge of the study’s parameters but explained that the study’s goal was to 

determine in a lab setting whether the DRE protocol served as a valid method of determining if 

people were under the influence of certain drugs. He affirmed that the study did not involve 

subjects actual driving motor vehicles. The DRE protocol tested subjects’ ability to multitask with 

divided attention which correlated to operating a vehicle under driving conditions. Deputy 

Schaller testified that the DRE protocol assisted law enforcement to recognize general signs and 

indicators of impairment by specific drugs because different drugs affect people in specific ways 

that can be recognized through the evaluation process. He conceded that the Bigelow Study stated 

that it did not represent a direct tested validity of the behavioral examination procedures for 

 

1 See National Highway Traffic Safety Administration, Identifying Types of Drug Intoxication: 

Laboratory Evaluation of a Subject-Examination Procedure, May 1985.

2 See National Highway Traffic Safety Administration, Field Evaluation of the Los Angeles Police 

Department Drug Detection Procedure, February 1986.
-4-

detecting and identifying drug intoxication in field situations but noted that it also stated that the 

study provided “valuable scientific information considering the potential accuracy and utility of 

such procedures.” Deputy Schaller repeated his explanation of the DRE 12-step process and how 

the totality of all the facts guided the formation of his opinion as to drug usage and impairment. 

He stated that the later toxicology report confirmed the presence of a drug substance in the 

suspects’ body but did not confirm the opinion of impairment.

Deputy Schaller also testified regarding the Compton Study which he stated had been 

conducted as a field study to evaluate whether the DRE process served as a valid and useful tool 

for trained law enforcement officers to determine drug impairment in motor vehicle drivers. He 

explained that the study’s subjects were people who had been arrested and were suspected of being 

under the influence. The Compton Study determined that the evaluators’ opinions regarding the 

173 subjects were 92.5% accurate in matching the blood testing results. The analysis revealed that 

49% were completely accurate opinions respecting 85 subjects, but 38% were partially accurate 

opinions respecting 65 subjects. He explained that some subjects had used a combination of drugs 

and the evaluators identified one but not all drugs because that one drug likely masked the other 

drug in the subjects’ systems. The blood tests revealed more than one drug, and therefore, the 

evaluators were deemed partially correct. Deputy Schaller affirmed that the study indicated that 

identification of marijuana through use of the DRE process had a 78% accuracy rate, but other 

drugs were identified at much lower percentages of accuracy. He explained that the law 

enforcement officers who participated in the field study derived their impairment opinions from 

the totality of their observations.

Deputy Schaller testified that the SFSTs were scientifically validated for determining 

alcohol intoxication and impairment by alcohol. He admitted that he did not know of any validated 

studies respecting detection of impairment by any other substances. He clarified that the two 

studies concluded that the DRE protocol is an accurate and reliable tool that enables law 

enforcement officers to make observations and then derive their impairment opinions based on the 

totality of the circumstances of the entire investigation. He conceded that to his knowledge the 

DRE protocol had not been scientifically validated for determination of drug impairment. When 

asked about a 2017 Report3to Congress by NHTSA regarding marijuana-impaired driving, after 

reviewing the report briefly, Deputy Schaller concurred that the report stated that studies had not 

shown that THC caused impairment on psychomotor tasks, cognitive, and executive functions as 

statistically significant impairments, and that it stated that the set of signs and symptoms, and 

physiological effects that are indicative of marijuana use were not based on driving impairment. 

Further, he agreed that the report stated that there were no current evidence-based methods for 

detecting marijuana-impaired driving.

Deputy Schaller affirmed that he prepared an evaluation form for defendant and explained 

that he concluded that defendant was impaired by marijuana based on the totality of the 

investigation from the time of the traffic stop, his encounter with defendant at the scene, his 

observation of defendant’s performance of the tests administered at the scene, interactions with 

 

3 Compton, Marijuana-Impaired Driving-A Report to Congress (July 2017) (DOT HS 812 440), 

Washington, DC: National Highway Traffic Safety Administration.
-5-

her, statements that she made, evidence in the vehicle, and then the DRE evaluation process. He 

explained that defendant exhibited visible signs of being under the influence of marijuana 

including marijuana odor coming from her person and from her vehicle, reddened bloodshot eyes, 

and she admitted using marijuana 30 minutes before the traffic stop. Deputy Schaller testified that 

he observed defendant’s performance of the SFSTs administered by Deputy White and observed 

defendant’s performance of the ARIDE tests Deputy Williams administered. Defendant also rated 

her degree of impairment as 3 on a scale of 1-10, where 1 signified no impairment and 10 signified 

the highest degree of impairment one could experience. Deputy Schaller considered relevant 

defendant’s admission of feeling impaired by the drug. Deputy Schaller explained that defendant 

was transported to the hospital where her blood was drawn and afterward he administered the drug 

evaluation. Deputy Schaller stated that at that point the law enforcement officers definitely had 

probable cause to believe that defendant was under the influence of drugs.

He testified that, before administering the DRE protocol, he had formed a common-sense 

judgment that defendant appeared under the influence of marijuana based on impairment

indicators. He then reiterated all of the observable general indicators and signs that indicate 

marijuana impairment and described how his experience and training enabled him to draw 

conclusions regarding marijuana-related impairment. He affirmed that he checked defendant’s 

pupils for dilation, her pulse rate, and blood pressure because those can be indicative of impairment 

by marijuana. He testified that defendant’s pupils, her pulse rate, and blood pressure were normal. 

He reiterated that he based his impairment opinion on the totality of the facts and indicators 

presented.

The district court issued a written opinion in which it first determined that Deputy White 

could testify as a lay witness regarding his contact with defendant and his administration of the 

SFSTs, but he could not testify as an expert regarding marijuana impairment because of the lack 

of consensus in the scientific community on the efficacy of using SFSTs to measure marijuana 

impairment. The district court opined that Deputy White’s testimony had probative value 

regarding defendant’s balance, coordination, and other skills necessary for safe operation of a 

motor vehicle. Similarly, the district court ruled that Deputy Williams could testify as a lay witness 

regarding his observations. The district court then considered whether Deputy Schaller could 

testify as a drug recognition expert and render a marijuana-impairment opinion under the 

requirements of MRE 702 and applicable caselaw. The district court reflected upon Deputy 

Schaller’s training and experience and the DRE program’s methodology that he used to evaluate 

defendant. The district court found that Deputy Schaller’s observations were not a scientific or 

medical diagnosis but were based upon physical signs and behaviors exhibited by defendant. The 

district court concluded that DRE training enabled officers to recognize observable signs, 

symptoms, and behaviors sufficient to permit the rendering of opinions on a defendant’s state of 

impairment. The district court found that the Bigelow Study and the Compton Study indicated 

that officers trained in DRE could identify specific drugs and impairment in the studies’ subjects 

with a high degree of accuracy which made the DRE program sufficiently reliable to meet the 

MRE 702 requirements. The district court found that Deputy Schaller had “been trained in 

accordance with the national standards and performed the DRE protocol proficiently.” The district 

court ruled as follows:

[Deputy Schaller] may testify as to his observations of a defendant’s acts, conduct, 

and appearance, and to give an opinion on the defendant’s state of impairment 
-6-

based on those observations. He may express an opinion that a suspect’s behavior 

and physical attributes are or are not consistent with the behavioral and physical 

signs associated with certain categories of drugs.

* * *

Deputy Schaller may testify as a DRE expert.

Defendant sought and the circuit court granted her leave to appeal the district court’sruling. 

The circuit court analyzed the evidence presented at the district court’s two-day hearing. The 

circuit court found that defendant’s toxicology report and her admission that she used marijuana 

30 minutes before the traffic stop indisputably established that she internally possessed marijuana, 

a controlled substance, while operating her motor vehicle. The court considered the applicable 

law and concluded that the standard of proof for a conviction of violation of MCL 257.625(1) 

required the prosecution to establish that defendant was “under the influence” while operating a

motor vehicle. The circuit court found that the NHTSA 2017 Marijuana-Impaired Driving-A 

Report to Congress indicated that no test available to law enforcement could determine driving 

impairment caused by marijuana use because the measurable amount of THC in a person did not 

correlate with impairment. The circuit court observed that trained DRE officers were being 

qualified as expert witnesses but no published Michigan case had addressed or decided the 

reliability and admissibility of testimony regarding application of the DRE protocol or opinion 

testimony that marijuana use affected a defendant’s ability to drive and to what degree.

The circuit court next considered whether the district court had properly exercised its 

gatekeeper role by correctly applying the three-part test under MRE 702 and the factors articulated 

in Daubert v Merrell Dow Pharm, Inc, 509 US 579, 592-593; 113 S Ct 2786; 125 L Ed 2d 469 

(1993), while recognizing the degree of latitude and discretionary authority trial courts have in 

determining an expert’s reliability as expressed in Kumho Tire Co, Ltd v Carmichael, 526 US 137, 

152-153; 119 S Ct 1167; 143 L Ed 2d 238 (1999), and People v Kowalski, 492 Mich 106, 120-

121; 821 NW2d 14 (2012). The circuit court noted that defendant argued that the DRE protocol 

lacked relevance and reliability because it did not do what it purported to do, i.e., prove that 

defendant’s marijuana intoxication affected her driving or rendered her “under the influence.”

The circuit court analyzed the DRE protocol functions and purpose and noted that its 

purpose was not to conclusively determine the presence of a particular drug which only a later 

toxicology test could reveal, but to determine whether a person is impaired at the time of the 

alleged violation and to opine which drug caused the impairment. The circuit court considered the 

DRE protocol 12-step process and noted that all DREs conduct it in the same standardized manner 

and record the results for each step on a standardized form. The circuit court found that only DRE 

trained officers who achieved a 75% corroboration rate were certified and that they were required 

to maintain a minimum accuracy rate and renew certification every two years.

The circuit court concluded that Deputy Schaller’s testimony regarding his application of 

the DRE protocol in the present case and his opinion that defendant had been under the influence 

of marijuana and unsafe to drive met the relevance and reliability requirements of MRE 702. The 

circuit court concluded from the record evidence that Deputy Schaller had the requisite training, 

specialized knowledge, and experience to identify behavioral and physiological signs of 
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impairment caused by different classes of drugs, plus 17 years’ experience as a road patrol deputy 

interacting with intoxicated drivers. The circuit court found that sufficient facts and data supported 

the validity of the DRE protocol and Deputy Schaller’s testimony regarding defendant’s marijuana 

intoxication. The circuit court concluded that Deputy Schaller formed his opinion based on 

reliable principles and methods and his testimony would assist the trier of fact in understanding 

the effects of marijuana intoxication and in determining a fact in issue. The circuit court observed 

that the degree of defendant’s intoxication remained a question for the trier of fact to decide as the 

ultimate arbiter of whether the prosecution proved all of the elements of the charged offense.

The circuit court also considered whether the probative value of Deputy Schaller’s 

proposed testimony would be substantially outweighed by unfair prejudice, confusion of the 

issues, misleading of the jury, or be needlessly cumulative. The court concluded that it would not. 

Respecting defendant’s argument that the testimony would be unfairly prejudicial because the jury 

would attribute undue and preemptive weight to it, the circuit court found no such danger because 

the trial court could instruct the jury to judge Deputy Schaller’s testimony by the same standard 

applicable to all witnesses and noted that he could be subjected to cross-examination and 

impeachment through presentation of contradictory evidence. The circuit court, therefore,

affirmed the district court’s ruling that Deputy Schaller qualified as an expert.

II. ANALYSIS

Defendant argues that the DRE protocol and its application in her case is inadmissible 

under MRE 702 because no studies correlate a DRE’s ability to determine the degree of 

impairment in someone who operates a motor vehicle after using marijuana. Defendant’s 

argument, although alluring, is unpersuasive.

The admissibility of expert testimony is governed by MRE 702 which provides:

If the court determines that scientific, technical, or other specialized 

knowledge will assist the trier of fact to understand the evidence or to determine a 

fact in issue, a witness qualified as an expert by knowledge, skill, experience, 

training, or education may testify thereto in the form of an opinion or otherwise if 

(1) the testimony is based on sufficient facts or data, (2) the testimony is the product 

of reliable principles and methods, and (3) the witness has applied the principles 

and methods reliably to the facts of the case.

“A court considering whether to admit expert testimony under MRE 702 acts as a 

gatekeeper and has a fundamental duty to ensure that the proffered expert testimony is both 

relevant and reliable.” Kowalski, 492 Mich at 120 (citation omitted). The court “must ensure that 

the [expert] testimony (1) will assist the trier of fact to understand a fact in issue, (2) is provided 

by an expert qualified in the relevant field of knowledge, and (3) is based on reliable data, 

principles, and methodologies that are applied reliably to the facts of the case.” Id. “The party 

proffering the expert’s testimony must persuade the court that the expert possesses specialized 

knowledge which will aid the trier of fact in understanding the evidence or determining a fact in 

issue.” People v Smith, 425 Mich 98, 112; 387 NW2d 814 (1986), citing MRE 702. Specialized 

knowledge must be something beyond the common knowledge of the average person. Kowalski, 

492 Mich at 123. An expert may be qualified by “knowledge, skill, experience, training, or 
-8-

education.” MRE 702. “MRE 702 requires the trial court to ensure that each aspect of an expert 

witness’s proffered testimony—including the data underlying the expert’s theories and the 

methodology by which the expert draws conclusions from that data—is reliable.” Gilbert v 

DaimlerChrysler Corp, 470 Mich 749, 779; 685 NW2d 391 (2004).

In its gatekeeping capacity, the trial court must make “a preliminary assessment of whether 

the reasoning or methodology underlying the testimony is scientifically valid and of whether that 

reasoning or methodology properly can be applied to the facts in issue.” Daubert, 509 US at 592-

593. This analysis does not hinge on discovering “absolute truth” or resolving “genuine scientific 

disputes.” Chapin v A & L Parts, Inc, 274 Mich App 122, 127; 732 NW2d 578 (2007). Even the 

Daubert court recognized the unreasonableness of expecting that an expert’s testimony “must be 

‘known’ to a certainty; arguably, there are no certainties in science.” Daubert, 509 US at 590.

Trial courts have broad latitude to consider whether the expert’s specialized knowledge or 

technique has been tested or subjected to peer review and publication, whether the known or 

potential rate of error has been determined, whether standards exist that control the technique’s 

operation, and the degree of general acceptance in the relevant expert community, as well as, other 

relevant factors as part of its determination of the reliability of the expert’s relevant testimony. Id. 

at 593-594; Kumho Tire, 526 US at 151-153. An expert may draw a conclusion from a set of 

observations based on extensive and specialized experience and knowledge. Kumho Tire, 526 US 

at 156. “[T]he trial court’s role as gatekeeper does not require it to search for absolute truth, to 

admit only uncontested evidence, or to resolve genuine scientific disputes.” People v Unger, 278 

Mich App 210, 217; 749 NW2d 272 (2008) (citation omitted). “The inquiry is not into whether 

an expert’s opinion is necessarily correct or universally accepted,” but “whether the opinion is 

rationally derived from a sound foundation.” Id. (citation omitted).

Defendant concedes that opinion testimony regarding whether a suspect was impaired 

would likely assist the trier of fact to determine a fact in issue at trial. She also concedes that 

Deputy Schaller completed the requisite training and education to be proficient in the DRE 

protocol. Defendant, however, takes issue with using the DRE analysis because the presence of a 

drug in a subject’s blood does not necessarily equate to impairment, and she contends that use of 

the DRE protocol cannot establish the degree of driving impairment with “scientific certainty.”

The record indicates that neither the prosecution nor Deputy Schaller represented to the 

lower courts that use of the DRE protocol, in and of itself, definitively establishes a person’s degree 

of impairment. Nor did Deputy Schaller testify that the DRE protocol’s use led to absolute 

certainty regarding a person’s drug impairment. Rather, the record indicates that the DRE protocol

serves as one of several tools law enforcement uses to determine if probable cause exists to charge 

a suspect of violation of MCL 257.625(1).

Evidence presented to the lower courts revealed that the DRE program is a nationally 

standardized protocol used by specially trained and certified law enforcement officers for 

identification of intoxication of persons by controlled substances within seven categories of drugs. 

Officers are trained to follow the 12-step protocol to observe behavioral and physiological 

indicators to determine the drug that the suspect may have used and assess the degree of 

impairment based on the totality of the officer’s relevant observations. The record does not reflect 

that any dispute exists regarding the indicators of marijuana intoxication which can include 
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observable physical evidence such as bloodshot eyes, eyelid tremors, pupil size, body tremors, 

body balance issues, and behavioral indicators such as inattention, inability to follow directions, 

inability to perform multiple tasks, and altered space and time perception. The record also 

indicates that NHTSA studies and data collected over many years confirm that the use of the DRE 

protocol methodology enables highly accurate conclusions regarding drug intoxication.

Defendant relies on some statements made in NHTSA’s 2017 Report to Congress to argue

that, because no tests have established the specific level of THC in a person’s blood that affects a 

person’s ability to safely operate a motor vehicle, the DRE testing protocol completely lacks 

reliability, requiring exclusion of Deputy Schaller’s testimony. The 2017 NHTSA Report 

indicates that, unlike alcohol, there is no chemical test for marijuana impairment that correlates

the level of THC in the blood with the degree of impairment. Consequently, THC blood test levels 

cannot serve as an indicator of driver impairment.

4

 Nevertheless, the Report acknowledges that 

smoking marijuana has been shown in many studies to affect a number of driving-related skills 

such as reaction time, tracking ability, lane position variability, decreased divided attention-target 

recognition, impaired cognitive performance like judgment, attention maintenance, impaired 

executive functioning, as well as impairment on psychomotor tasks.5 Although the Report 

recognizes limitations of the DRE testing protocol because no chemical based impairment standard

exists, and that it cannot serve alone as an impairment determiner, the Report, nevertheless,

acknowledges that the DRE program serves as an aid in law enforcement investigations of 

suspected drug-impaired driving cases where properly trained officers follow good investigatory 

techniques and carefully document their factual observations.

6

 The Report does not assert 

anywhere that law enforcement should not use DRE trained and certified officers as part of drugimpaired driving case investigation. Rather, it endorses the DRE program as the highest level of 

training an officer can receive to “identify the signs and symptoms of drug use that could be used 

to determine whether a suspected driver was impaired by drugs and to rule out possible causes 

such as neurological deficits, diseases, and illness.”

7

 The Report is not dispositive on whether the 

district court erred by qualifying Deputy Schaller as an expert or the circuit court’s affirmance of 

that decision. I find defendant’s arguments go to the weight of Deputy Schaller’s testimony but 

not its admissibility.

As explained in Kumho Tire, an “expert might draw a conclusion from a set of observations 

based on extensive and specialized experience.” Kumho Tire, 526 US at 156. Examination of the 

record in this case reveals that Deputy Schaller had numerous years’ experience as a sheriff’s 

deputy serving on road patrol during which he investigated and apprehended suspected drug-

 

4 Marijuana-Impaired Driving-A Report to Congress, at 7, 11, 13, 27-29.

5

Id. at 11, 13, 22.

6

Id. at 9, 27-28. The Report states:

The lack of an “impairment standard” equivalent to BAC level does not prevent the 

successful prosecution of a marijuana-impaired driver. The lack of toxicological 

evidence simply means that the officer has to offer other evidence that the driver 

was under the influence of marijuana too impaired to drive safely. [Id. at 28.]

7

Id. at 28.
-10-

impaired drivers. He had training and experience in administering SFSTs, was ARIDE certified, 

and trained and certified in the DRE program, and had administered the DRE testing protocol in 

the field numerous times. His conclusions regarding driver drug usage and impairment were 

confirmed in a very high percentage of the cases. The record confirms the district court’s and 

circuit court’s conclusions that Deputy Schaller had the requisite training, specialized knowledge, 

and experience to identify behavioral and physiological signs of impairment caused by different 

classes of drugs, plus 17 years’ experience as a road patrol deputy interacting with intoxicated 

drivers.

Respecting the sufficiency of the facts and data on which Deputy Schaller relied, he

testified regarding the manner in which he conducted his investigation in this case which included 

attending the scene and observing defendant’s traffic stop, observing her bloodshot eyes, smelling 

the odor of marijuana on her person and in her car, observing her deficient performance of the 

SFSTs administered by Deputy White, observing her deficient performance of the tests

administered by Deputy Williams, and observing defendant and collecting data during his

administering of the DRE protocol. Deputy Schaller followed the applicable steps in the DRE 

protocol and documented his findings. Deputy Schaller also considered defendant’s admissions

to the investigating officers that she smoked marijuana 30 minutes before the traffic stop and 

admitted to the officers in Deputy Schaller’s presence that she felt impaired at level 3 on a scale 

of 1-10. Deputy Schaller considered all of these facts and data obtained during the investigation 

and concluded that defendant had operated her motor vehicle while under the influence of 

marijuana and had been impaired to the extent that she could not safely operate her vehicle. 

Defendant hasfailed to establish that the facts and data obtained during the investigation by Deputy 

Schaller lacked accuracy or sufficiency for an experienced law enforcement officer to form an 

opinion. She does not challenge the deficiencies of her performance of the various tests. Nor does 

she dispute Deputy Schaller’s testimony that he based his opinions upon the totality of the 

circumstances, not merely the application of the DRE protocol. The record indicates that Deputy 

Schaller derived his conclusions by applying standardized principles and valid investigative 

methods to the facts of this case.

I conclude that the district court did not abuse its discretion by finding that sufficient facts 

and data supported the validity of the DRE protocol and Deputy Schaller’s testimony regarding 

defendant’s marijuana intoxication based upon the totality of the circumstances. Likewise, the 

circuit court correctly concluded that Deputy Schaller formed his opinions based on reliable 

principles and methods and properly concluded that his testimony would assist the trier of fact in 

understanding the effects of marijuana intoxication and in determining a fact in issue. The circuit 

court also correctly understood that the degree of defendant’s intoxication remained a question for

the trier of fact to decide in relation to its determination whether the prosecution proved all of the 

elements of the charged offense.

The record supports the district court’s and the circuit court’s conclusions that Deputy 

Schaller’s testimony is based on sufficient facts and data collected during the investigation, that 

his testimony is the product of reliable investigatory principles and methods, and that he applied 

those principles and methods to the fact of this case. The record also supports the courts’ respective 

conclusions that Deputy Schaller’s testimony will assist the trier of fact to understand a fact in 

issue. I conclude that Deputy Schaller’s testimony meets the requirements of MRE 702 and 

applicable law and is admissible. Moreover, to the extent that any concerns exist regarding how 
-11-

the jury should understand his testimony, Deputy Schaller would be subjected to crossexamination and the trial court can ably instruct the jury regarding its consideration of his 

testimony.

Accordingly, in my opinion, the district court did not abuse its discretion by qualifying 

Deputy Schaller as an expert to testify regarding whether defendant operated her motor vehicle 

while under the influence of marijuana and impaired to a degree that made her unable to safely 

operate her motor vehicle. The circuit court did not err by affirming the district court’s decision. 

Accordingly, I would affirm.

/s/ James Robert Redford