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

9:25 a.m.

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.

BORRELLO, P.J.

In this prosecution for operating while intoxicated (OWI), MCL 257.625(1)(a), defendant 

Cara Christine Bowden appeals by interlocutory leave granted1the circuit court’s order affirming 

the district court’s order qualifying Ottawa County Sheriff’s Department deputy Adam Schaller as 

an expert drug recognition evaluator (DRE)2and holding that Schaller could provide an opinion 

whether defendant operated her vehicle under the influence of marijuana to a degree that rendered 

her unsafe to drive. For the reasons set forth in this opinion, we reverse and remand.

I. BACKGROUND

On December 1, 2020, defendant was stopped by Ottawa County Sheriff’s Department 

deputy Monte White for driving with only one working headlight. White was working with 

Schaller at the time of the traffic stop. According to his testimony, Schaller was certified in 

Advanced Roadside Impaired Driving Enforcement (ARIDE). White testified at the evidentiary 

 

1 People v Bowden, unpublished order of the Court of Appeals, entered September 9, 2021 (Docket 

No. 357976).

2 The record contains indications both that DRE stands for “Drug Recognition Evaluator” and 

“Drug Recognition Expert.” We need not resolve this discrepancy on the proper nomenclator. 

Instead, we will simply use the abbreviation “DRE” for the sake of simplicity. Furthermore, even 

if Schaller’s certification designates him to be a drug recognition “expert,” that label has no bearing 

on whether he may properly testify as an expert for purposes of MRE 702.
-2-

hearing that when he approached defendant, he smelled “an odor of marijuana coming from the 

driver window and . . . noticed that [defendant’s] eyes were bloodshot-red.” White asked 

defendant to get out of the vehicle, and White proceeded to administer standardized field sobriety 

tests (SFSTs). Another Ottawa County Sheriff’s Deputy, Brian Williams, arrived on the scene. 

After Williams’ arrival at the scene of the stop, Williams administered two additional tests. When 

questioned, defendant stated that she smoked marijuana approximately 30 minutes earlier. 

Schaller observed as defendant completed the tests administered by White and Williams. White 

testified that he did not observe defendant commit any lane, speed, or other moving violations 

while she was driving before he initiated the traffic stop. According to Schaller, defendant was 

asked to rate her “personal feelings of impairment” on a scale of 1 to 10, with “1 being not at allimpaired and 10 being the most high (sic) that somebody could ever be.” Schaller testified, “she 

personally self-rated herself as feeling at a 3, in terms of a scale of 1 to 10.” Defendant was arrested 

and taken to a hospital to have her blood drawn. At the hospital, Schaller administered a DRE 

evaluation to defendant. Defendant was charged with operating while intoxicated.

As relevant to the issue presented on appeal, the prosecution filed a motion in the district 

court requesting the court to “declare Deputy Adam Schaller an expert in the field of Drug 

Evaluation and Classification and be allowed to testify, and provide an expert opinion, as a Drug 

Recognition Expert.” Defendant opposed this motion.

At the evidentiary hearing, Schaller testified that in addition to SFST and ARIDE training,

he had completed a DRE training and certification program in 2019. Schaller explained that the 

DRE program was a “months’ long process” that consisted of “80-plus hours of classroom work 

where you’re instructed in different medical conditions, observable signs of drug impairment, 

different types of drugs, [and] biological factors,” followed by field work performing the tests and 

a final examination. Schaller testified that based on his application of the DRE protocols to 

defendant and the “totality of the circumstances,” he opined that defendant was impaired by, or 

under the influence of, marijuana and unable to safely drive a motor vehicle at the time of the 

traffic stop.

In his testimony, Schaller described the DRE protocol in detail. There are 12 steps: a 

preliminary breath test, an interview with the arresting officer, a preliminary examination and first 

pulse check, an eye examination, multiple divided attention tests, a vital signs and second pulse 

check, an examination of pupil sizes in various lighting conditions, an examination of muscle tone, 

a check for injection sights and third pulse check, an interrogation, the DRE officer’s formation of 

an opinion based on the totality of the facts gathered in the previous 10 steps, and the completion 

of a laboratory toxicology report. There are 7 drug categories identified by the protocol: central 

nervous system depressants, central nervous stimulants, hallucinogens, dissociative anesthetics, 

narcotic analgesics, inhalants, and cannabis.

Schaller also explained the reasons for completing each of the 12 steps. The preliminary 

breath test is conducted to determine whether the person is under the influence of alcohol. An 

interview of the arresting officer provides facts and observations about the subject from the scene 

in instances where Schaller, as the DRE investigator, was not present for the traffic stop and arrest. 

The preliminary interview involves asking the subject about medical conditions, physical 

conditions, and medications that may make the subject appear “impaired when they’re not.” 

During this step, the DRE investigator also makes observations of any visible signs of impairment 
-3-

and checks the subject’s pulse for the first time. The eye examination includes checking for 

horizontal and vertical gaze nystagmus and the eyes’ ability to converge on an object approaching 

the face. Next, the subject is administered a series of four tests intended to measure the subject’s 

abilities to divide attention, complete multiple tasks, follow directions, accurately perceive time, 

and maintain physical body control and balance. Schaller explained that these divided attention 

tests were relevant to a subject’s driving ability because driving a vehicle requires a driver to divide 

attention, multi-task, and accurately perceive time and distance to share the road with other 

vehicles. Further, Schaller testified that the various physical examinations were completed 

because different substances had different physical effects on the body that could be observed 

during these examinations. 

Schaller admitted that the 2018 SFST manual published by NHTSA3indicated that the 

SFSTs, which were also administered as part of the DRE protocol,4had only been validated for 

indicating impairment by alcohol or a person’s blood alcohol content. Schaller did not know of 

any scientific studies validating the use of the SFSTs for determining a person’s level of 

impairment by any other substance.

According to Schaller, the DRE protocol was developed by the Los Angeles Police 

Department in the late 1970s. Schaller further testified about studies that were conducted 

regarding the protocol:

So, in 1984, John Hopkins University with [the] National Highway Traffic 

Safety Administration [NHTSA] performed a lab validation study where they had 

volunteers who were dosed with different categories of drugs at different levels

who were evaluated by DRE’s from the Los Angeles Police Department and 

through that process they were able to determine, like, a success and error rate and 

showing that they had a high success rate. And then after that, in 1985, they did a 

field validation study with the Los Angeles Police Department where 173 

individuals who were arrested for impaired driving offenses other than alcohol

where blood was collected were evaluated by Drug Recognition Experts, and that 

was also able to determine an error rate and a positivity rate where they were able 

to determine the program -- the program validity.

Schaller further explained, however, that the studies found the DRE protocol to be

successful in determining that a person was “not impaired” but that “in determining that somebody 

is impaired and to which drug category that they’re impaired, they were able to -- the error rate 

would be what they were not able to opine.” Schaller stated that the goal of the first study “was to 

determine whether or not the protocol was a valid method of determining whether people were 

under the influence . . . of certain drug categories.” The study did not test actual driving ability. 

According to Schaller, the “key finding” of the 1985 field study “was that the DBCP, Drug 

Evaluation Classification Program, or DRE process or program is a reliable tool for law 

 

3 The referenced portions of this manual were admitted into evidence.

4 According to Schaller, the SFSTs are incorporated within the divided attention tests of the DRE 

protocol.
-4-

enforcement to investigate and determine impairment.” Schaller also admitted that a substance 

like marijuana could be present in person’s body without rendering that person “impaired” or 

“under the influence.” Schaller testified:

So, the goal of this program is not to correlate the presence of a substance 

to impairment; it’s to observe the subject, their demeanor, their physical signs of 

general indicators of impairment and their performance in a psychophysical test to 

determine whether or not they are impaired. We use that information that we see 

to help us determine which type of drug they’re -- of the seven categories that 

they’re impaired by. The -- whether or not there’s a drug active in their system is 

-- is only used to confirm -- a confirmatory lab to show that our observations of the 

person were -- were valid or correct.

The studies referenced by Schaller were admitted into evidence. The conclusion section 

of the report for the earlier laboratory study states that “[t]his laboratory simulation study does not 

represent a direct test of the validity of these or related behavioral examination procedures for 

detecting and identifying drug intoxication in field situations.” This study found that the protocol 

was highly accurate in correctly identifying the class of drug that a subject had taken when the 

evaluator judged the subject to be intoxicated. The study also found that the likelihood that a 

subject who had been given an active drug would be judged intoxicated by a DRE evaluator 

depended on the dose of the drug received and that “[j]udgments of drug intoxication were more 

likely at the higher doses of active drug than at the lower doses.”

In the subsequent field study, the report concluded that “DREs were fairly accurate in 

determining which drug or drug class the suspect had taken.” However, the following quotation 

from the report succinctly illustrates the limitations of this study as relevant to the issues currently 

before this Court on appeal:

This section discusses the accuracy of the DREs decisions regarding which

specific drugs the suspects were under the influence of. It is important to remember 

that the DREs in this study were examining the suspects for law enforcement

purposes. The DREs indicated whether they felt the suspects were “impaired” by

drugs (and hence “unable to operate a motor vehicle safely”), and if so, what

specific drugs (or drug classes) the suspect was “impaired” by.

There is no way to determine objectively whether the suspects were actually

too “impaired” to drive safely. The fact that drugs were found in a suspect’s blood 

does not necessarily mean the suspect was too impaired to drive safely. Contrary 

to the case with alcohol, we do not know what quantity of a drug in blood implies 

impairment. Thus, this study can only determine whether a drug was present or

absent from a suspect’s blood when the DRE said the suspect was impaired by that 

drug. (emphasis added).

Furthermore, the report also stated:

This field evaluation of the LAPD drug recognition procedure was designed 

to determine whether trained officers could accurately judge the presence of drugs 
-5-

other than alcohol in impaired driving suspects, and whether the screening 

procedure allowed the officers to differentiate between different drugs (or drug 

classes).

* * *

The results of the two studies conducted by NHTSA appear to show that the 

LAPD drug recognition procedure provides the trained police officer with the 

ability to accurately recognize the symptoms of many types of drug use by drivers. 

When the officers identify a suspect as having used particular drugs a blood test 

almost always will confirm their judgement.

A 2017 report from the NHTSA to Congress, titled Marijuana-Impaired Driving - A Report 

to Congress, was also admitted into evidence at the hearing. This report began by comparing what 

is known about marijuana-impaired driving with what is known about alcohol-impaired driving 

because “the effects of alcohol on driving performance and crash risk are relatively well 

understood.” Noting the intense interest and wealth of research studies devoted to alcoholimpaired driving over a more than 60-year period, the report explained how alcohol is absorbed 

and eliminated by the body and summarized the well-established correlation between alcohol 

concentration in the blood or breath and the degree to which driving skills become impaired. The 

research establishing this correlation involved “studies of alcohol-impaired driving related skills, 

primarily through laboratory studies involving subjects dosed on alcohol, using psychomotor tasks 

(reaction time, tracking, target detection), driving simulators and drivers on closed courses in 

instrumented vehicles, epidemiological studies including roadside surveys of alcohol use by 

drivers, and studies of alcohol use by crash-involved drivers.”

In contrast, the report explains, marijuana is processed by the body in significantly different 

ways and the effects of marijuana use on driving-related skills have yet to be extensively studied. 

According to the report, there was research that had “demonstrated the potential of marijuana to 

impair driving related skills,” but the research did not show a relationship between impairment and 

levels of delta-9-tetrahydrocannabinal (THC).

5

 Studies examining the relationship between THC 

blood levels and degree of impairment had consistently found that “the level of THC in the blood 

and the degree of impairment do not appear to be closely related” and that “[p]eak impairment 

does not occur when THC concentration in the blood is at or near peak levels.” Further, “[p]eak 

THC level can occur when low impairment is measured, and high impairment can be measured 

when THC level is low.” The report also indicated that “[c]urrent knowledge about the effects of 

marijuana on driving is insufficient to allow specification of a simple measure of driving 

impairment outside of controlled conditions” and that “there are currently no evidence-based 

methods to detect marijuana-impaired driving.” The report’s general conclusion as relevant to the 

issues currently before us is aptly summarized in the following quotation:

Currently, there is no impairment standard for drivers under the influence 

of marijuana. Many of the reasons for this are discussed elsewhere in this report. 

They include the fact that there is no chemical test for marijuana impairment, like 

 

5 THC is the primary psychoactive substance in marijuana.
-6-

a BAC or BrAC test for alcohol that quantifies the amount of alcohol in their body, 

indicates the degree of impairment, and the risk of crash involvement that results 

from the use of alcohol. The psychoactive ingredient in marijuana, delta-9-

tetrahydrocannabinal (THC), does not corelate well with impairment. . . .

Without a chemical test, the alternative is to develop a psychomotor, 

behavioral or cognitive test that would indicate the degree of driving impairment 

and elevated risk of crash involvement due to marijuana use. As was described 

earlier in this report, marijuana has been show [sic] to impair critical driving related 

skills including psychomotor abilities like reaction time, tracking ability, and target

detection, cognitive skills like judgment, anticipation, and divided attention, and 

executive functions like route planning and risk taking. However, available 

research does not support the development of such a psychomotor, behavioral or 

cognitive test that would be practical and feasible for law enforcement use at this 

time. It is certainly possible that when more research has been conducted on the 

impairing effects of marijuana use on driving, that can be shown to increase the risk 

of crash involvement, that it may be possible to develop such a test in the future.

NHTSA, and others, are currently conducting research toward that goal. We are 

funding a controlled dosing study of different ways to measure marijuana 

impairment in driving related skills in the hope that some of these measures will be 

amenable to use by law enforcement. The first step is to show that everyone dosed 

on marijuana shows an observable amount of impairment in a controlled laboratory 

setting. The next step would be to develop simplified versions of these measures 

that do not require sophisticated and expensive equipment that are suitable for field 

use by law enforcement. The last step would be to establish the relationship 

between the observed impairment on these tests and elevated risk of crash 

involvement. Success in the near term is not guaranteed, but possible.

The district court concluded that Deputy Schaller could testify as “a DRE expert.” 

Specifically, the district court found that based on the two studies of the DRE program from the 

1980s, the DRE program was “sufficiently reliable to meet the requirements of MRE 702.” The 

district court further stated in relevant part:

The court finds Deputy Schaller has been trained in accordance with the 

national standards and he performed the DRE protocol proficiently. He 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 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.

Defendant was granted leave to appeal to the circuit court, and the circuit court affirmed 

the district court’s order. The circuit court concluded that Schaller’s testimony regarding the DRE 

protocol satisfied the relevance and reliability requirements of MRE 702 based on the evidence 

submitted at the hearing in the district court and based on the acceptance of the DRE program by 

courts in other jurisdictions.
-7-

This Court subsequently granted defendant leave to appeal the circuit court’s order.

II. STANDARD OF REVIEW

An appellate court reviews a lower court’s decision to admit or exclude expert testimony 

for an abuse of discretion. People v Dobek, 274 Mich App 58, 93; 732 NW2d 546 (2007). An 

abuse of discretion occurs when the court’s decision falls outside the range of reasonable and 

principled outcomes. People v Unger, 278 Mich App 210, 217; 749 NW2d 272 (2008). We review 

de novo preliminary questions of law, such as whether a rule of evidence precludes the admission 

of particular evidence and any issues involving interpretation of the Michigan Rules of Evidence. 

People v Muhammad, 326 Mich App 40, 47; 931 NW2d 20 (2018); Dobek, 274 Mich App at 93. 

“A trial court necessarily abuses its discretion when the court permits the introduction of evidence 

that is inadmissible as a matter of law.” Dobek, 274 Mich App at 93.

III. ANALYSIS

Defendant maintains on appeal that the proposed expert testimony of Schaller regarding

his application of the DRE protocol and the opinion he formed of defendant’s state of impairment 

due to marijuana is inadmissible under MRE 702.

MRE 702 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. 

MRE 702 imposes an obligation on the trial court to ensure that any expert testimony that 

is admitted at trial is reliable. Gilbert v DaimlerChrysler Corp, 470 Mich 749, 780; 685 NW2d 

391 (2004). Although the exercise of this gatekeeper role is within a trial court’s discretion, the 

court may neither abandon this role nor perform it inadequately. Id. Under MRE 702, the trial 

court is required 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.” Id. at 779.

“MRE 702 incorporates the standards of reliability that the United States Supreme Court 

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

(1993), in interpreting the equivalent federal rule of evidence.” Muhammad, 326 Mich App at 51-

52. 

Under Daubert, a trial court must “determine at the outset . . . whether the expert is 

proposing to testify to (1) scientific knowledge that (2) will assist the trier of fact 

to understand or determine a fact in issue.” Daubert, 509 US at 592. “This entails 

a preliminary assessment of whether the reasoning or methodology underlying the 

testimony is scientifically valid and of whether that reasoning or methodology 
-8-

properly can be applied to the facts in issue.” Id. at 592-593. Some factors that 

bear on the trial court’s inquiry include: (1) whether the scientific knowledge or 

technique can, and has been, tested, (2) “whether the theory or technique has been 

subjected to peer review and publication,” (3) “the known or potential rate of error,”

(4) “the existence and maintenance of standards controlling the technique’s 

operation,” and (5) whether there is “general acceptance” of the scientific 

technique. Id. at 593-594. However, these factors are not exclusive; instead, 

“[m]any factors will bear on the inquiry . . . .” Id. at 593. [Muhammad, 326 Mich 

App at 52 (ellipses in original).] 

This inquiry is a “flexible” one that must focus “solely on principles and methodology”

employed, “not on the conclusions that they generate.” Daubert, 509 US at 594-595. Under MRE 

702 and Daubert, “the trial court’s role as a gatekeeper does not require it to search for absolute 

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

Mich App at 217 (quotation marks and citation omitted). Rather, the trial court’s role is to filter 

out evidence that is unreliable, with the relevant inquiry being “whether the opinion is rationally 

derived from a sound foundation.” Id. (quotation marks and citation omitted). “Daubert’s general 

holding—setting forth the trial judge’s general ‘gatekeeping’ obligation—applies not only to 

testimony based on ‘scientific’ knowledge, but also to testimony based on ‘technical’ and ‘other 

specialized’ knowledge.” Kumho Tire Co, Ltd v Carmichael, 526 US 137, 141; 119 S Ct 1167; 

143 L Ed 2d 238 (1999). The party offering the expert testimony bears the burden of satisfying 

the preconditions of MRE 702 and establishing admissibility of the proposed evidence. Gilbert, 

470 Mich at 781, 789.

Defendant was charged in this case with OWI under MCL 257.625(1)(a), which provides 

as follows:

(1) A person, whether licensed or not, shall not operate a vehicle on a 

highway or other place open to the general public or generally accessible to motor 

vehicles, including an area designated for the parking of vehicles, within this state 

if the person is operating while intoxicated. As used in this section, “operating 

while intoxicated” means any of the following:

(a) The person is under the influence of alcoholic liquor, a controlled 

substance, or other intoxicating substance or a combination of alcoholic liquor, a 

controlled substance, or other intoxicating substance. [Emphasis added.]

To prove a person was “under the influence” of alcoholic liquor, a controlled substance, or 

other intoxicating substance, the prosecution “must prove that defendant’s ability to drive was 

substantially and materially affected by consumption” of the relevant substance. People v 

Lambert, 395 Mich 296, 305; 235 NW2d 338 (1975) (quotation marks omitted); see also People v 

Dupre, 335 Mich App 126, 131-132; 966 NW2d 200 (2020).

Here, defendant argues that the prosecution “has yet to point to a study that correlates the 

opinion of a DRE evaluator to actual degradation of a subjects’ ability to safely operate a motor 

vehicle.” Defendant and amicus contend that the DRE protocol has not been validated as a reliable 

tool for determining whether a person’s ability to drive has been impaired by marijuana and that 
-9-

Schaller’s opinion is thus inadmissible under MRE 702 because it is based on unreliable principles

and methodologies. Defendant argues that 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. We 

agree.

It is apparent from the record that the prosecution did not present any evidence in the 

district court to show that the DRE protocol had been validated as a reliable method for 

demonstrating a person’s level of impairment due to marijuana or the degree to which a person’s 

driving abilities could be diminished by any given level of marijuana. The studies relied on by the 

prosecution demonstrated the DRE protocol’s level of accuracy with respect to determining 

whether a particular type of substance was present in a person’s blood, but neither of the submitted 

reports purported to even address the question of how particular levels of marijuana impacted a 

person’s ability to drive or rendered a person “impaired.” Indeed, the determination under the 

DRE protocol that a person is “impaired” and unable to safely drive a car appears to be ultimately 

based on the DRE officer’s subjective judgment, and there is no evidence in this record that the 

ability of a person to make such a judgment based on the application of the DRE protocol has been 

tested to demonstrate the accuracy and validity of reaching such a conclusion on a person’s level 

of impairment due to marijuana. 

Additionally, in the 2017 report to Congress, the NHTSA wrote that, although research has 

shown that marijuana has the potential to impair one’s ability to drive, there were “currently no 

evidence-based methods to detect marijuana-impaired driving.” This report also stated that the 

available research did not yet support the development of a practical and feasible “psychomotor, 

behavioral or cognitive test that would indicate the degree of driving impairment and elevated risk 

of crash involvement due to marijuana use.” 

It bears repeating that the earlier field study—on which the prosecution relies—contained

the following disclaimer:

This section discusses the accuracy of the DREs decisions regarding which

specific drugs the suspects were under the influence of. It is important to remember 

that the DREs in this study were examining the suspects for law enforcement 

purposes. The DREs indicated whether they felt the suspects were “impaired” by 

drugs (and hence “unable to operate a motor vehicle safely”), and if so, what 

specific drugs (or drug classes) the suspect was “impaired” by.

There is no way to determine objectively whether the suspects were actually 

too “impaired” to drive safely. The fact that drugs were found in a suspect’s blood 

does not necessarily mean the suspect was too impaired to drive safely. Contrary 

to the case with alcohol, we do not know what quantity of a drug in blood implies 

impairment. Thus, this study can only determine whether a drug was present or 

absent from a suspect’s blood when the DRE said the suspect was impaired by that 

drug.

The prosecution did not present any evidence that the DRE protocol has been tested, or has 

a known error rate, with respect to the purpose for which the prosecution intended to use the results
-10-

of the protocol in this case—to provide evidence of defendant’s level of impairment and impaired 

driving ability. Muhammad, 326 Mich App at 52. There simply is no evidence in this record to 

support that the DRE protocol can reliably be used to detect the degree or level of intoxication 

caused by marijuana and determine whether that level of intoxication has made the person unable 

to safely drive a motor vehicle. Our Supreme Court has explained that because “MRE 702 

mandates a searching inquiry, not just of the data underlying expert testimony, but also of the 

manner in which the expert interprets and extrapolates from those data,” it is therefore “insufficient 

for the proponent of expert opinion merely to show that the opinion rests on data viewed as 

legitimate in the context of a particular area of expertise . . . .” Gilbert, 470 Mich at 782. “The 

proponent must also show that any opinion based on those data expresses conclusions reached 

through reliable principles and methodology.” Id. Moreover, the court’s “gatekeeping inquiry 

must be tied to the facts of a particular case,” Kumho Tire, 526 US at 150 (quotation marks and 

citation omitted), and there must be “ ‘a valid . . . connection to the pertinent inquiry as a 

precondition to admissibility,’ ” id. at 149, quoting Daubert, 509 US at 592 (ellipsis in original). 

Here, the prosecution has failed to establish any valid connection between the use of the DRE 

protocol and a conclusion regarding the degree to which a person’s driving ability was diminished 

by the use of marijuana.

It is clear from the very evidence which they presented to the district and circuit courts that 

the prosecution failed to meet its burden to establish the reliability, and thus the admissibility, of 

the proposed expert testimony. Gilbert, 470 Mich at 779-781, 789; Muhammad, 326 Mich App at 

52. Therefore, the proposed expert testimony was inadmissible under MRE 702.6

Reversed and remanded for further proceedings consistent with this opinion. We do not 

retain jurisdiction.

/s/ Stephen L. Borrello 

/s/ Michael J. Kelly

 

6 We note that this conclusion does not preclude the prosecution from introducing Schaller’s 

testimony as a lay witness to the extent that testimony is otherwise not inadmissible. Contrary to 

the apparent concern of our dissenting colleague, our holding is not a blanket prohibition on 

Schaller’s testimony. We simply hold that Schaller cannot provide expert testimony under MRE 

702 regarding his application of the DRE protocol and the opinion he formed of defendant’s state 

of impairment due to marijuana.