State v. Anderson: No Isomer Distinction—l‑Methamphetamine Is a Schedule II Substance; Broad Trial-Court Discretion Over Daubert Hearings and Expert Disclosures

Court: Supreme Court of South Dakota

Citation: 2025 S.D. 45 (No. #30870-a-SPM)

Date: August 13, 2025

Author: Justice Myren (Chief Justice Jensen and Justices Kern, Salter, and Devaney concurring)

Introduction

This case presents three interrelated trial-management and evidentiary issues often encountered in drug-ingestion prosecutions: (1) how strictly courts may enforce expert disclosure deadlines; (2) when a Daubert hearing is required to vet forensic toxicology evidence based on established methodologies; and (3) whether a defendant’s fair-trial right is infringed when courts limit expert testimony and exclude late-disclosed experts.

Scott E. Anderson was found asleep in the driver’s seat of a vehicle at 3:00 a.m. with the brake lights illuminated. After field sobriety testing and a consensual blood and urine collection, both samples tested positive for carboxy-THC, amphetamine, and methamphetamine via gas chromatography mass spectrometry (GCMS) at the South Dakota Public Health Laboratory. Anderson’s defense focused on laboratory reliability and, in particular, the lab’s failure to distinguish between the d- and l- isomers of methamphetamine (with the defense suggesting l‑methamphetamine can be an OTC medication component).

The circuit court (Judge Michelle K. Comer) denied a Daubert hearing, excluded a late-disclosed defense expert (forensic toxicologist Sarah Urfer), limited testimony from the defense’s pharmacist expert (Valeri Silva) as to laboratory error margins, and (before a State witness “opened the door”) initially precluded isomer evidence as legally immaterial. A jury convicted Anderson of unauthorized ingestion of a controlled substance and of driving or being in physical control of a vehicle while under the influence. On appeal, Anderson challenged: (1) exclusion/limitation of defense experts; (2) denial of a Daubert hearing; and (3) alleged denial of a fair trial. The Supreme Court affirmed.

Summary of the Opinion

Expert disclosure and exclusion: The circuit court acted within its discretion in enforcing a pretrial disclosure order and excluding the defense toxicology expert (Urfer) disclosed after the court-imposed deadline. Labeling an expert as “rebuttal” does not excuse disclosure when the party intends to use the expert in its case-in-chief.
Limitation of pharmacist expert testimony: Limiting the pharmacist (Silva) to her demonstrated expertise (OTC medications and isomer presence) and precluding her testimony on laboratory “margin of error” was proper; forensic toxicology quantification error rates fall outside her qualifications and, in any event, the “±20%” at issue describes a quantitation range, not a misidentification probability.
Daubert hearing: No abuse of discretion occurred in denying a Daubert hearing. GCMS is a well-established, widely used method; the chemists’ credentials were adequate; and no evidence showed a novel theory, unusual technique, or improper application warranting a pretrial reliability hearing.
No denial of a fair trial: Anderson’s core defense—that l‑methamphetamine is not a controlled substance—was legally incorrect under SDCL 34‑20B‑16, which includes methamphetamine’s isomers. He nevertheless presented substantial evidence and cross-examination touching on his theory. There was no due process violation.
Clarified statutory point of law: Under SDCL 34‑20B‑16, methamphetamine and its isomers (including l‑methamphetamine) are Schedule II substances; the State need not differentiate isomers to prove unauthorized ingestion (SDCL 22‑42‑5.1).

Analysis

Precedents Cited and Their Role in the Court’s Decision

State v. Machmuller, 2001 S.D. 82, 630 N.W.2d 495; State v. Edelman, 1999 S.D. 52, 593 N.W.2d 419. These decisions reaffirm the broad discretion vested in trial courts to determine expert qualifications and to admit expert testimony. They set the stage for reviewing the exclusion of a late-disclosed toxicology expert and the scope of a pharmacist’s permissible opinions.
State v. Carter, 2023 S.D. 67, 1 N.W.3d 674; State v. Snodgrass, 2020 S.D. 66, 951 N.W.2d 792; State v. Loeschke, 2022 S.D. 56, 980 N.W.2d 266; Owens v. Russell, 2007 S.D. 3, 726 N.W.2d 610. These authorities define “abuse of discretion” and articulate the prejudice standard: even if an evidentiary ruling is erroneous, reversal requires a showing of a reasonable probability of a different outcome.
United States v. Watkins, 66 F.4th 1179 (8th Cir. 2023); State v. Guzman, 2022 S.D. 70, 982 N.W.2d 875. While recognizing a criminal defendant’s fundamental right to present witnesses and a defense, these cases underscore that this right is not absolute; it yields to legitimate trial management interests such as orderly disclosure.
SDCL 23A‑45‑13. This statutory grant of authority allowed the circuit court to impose pretrial disclosure obligations where no specific procedure is prescribed, validating the witness/exhibit deadline and the exclusion of untimely-disclosed experts.
Schrader v. Tjarks, 522 N.W.2d 205 (S.D. 1994). The defense’s reliance on a general principle that rebuttal witnesses need not be disclosed was cabined. The Court clarified that the cited principle governs the rebuttal phase of trial (per SDCL 15‑14‑1) and does not excuse disclosure when a party intends to call the witness in its case-in-chief to challenge reliability.
State v. Jackson, 2020 S.D. 53, 949 N.W.2d 395; Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993); Burley v. Kytec Innovative Sports Equip., Inc., 2007 S.D. 82, 737 N.W.2d 397; Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999); United States v. Kenyon, 481 F.3d 1054 (8th Cir. 2007); State v. Moeller, 2000 S.D. 122, 616 N.W.2d 424. Collectively, these authorities establish that trial courts have latitude to determine how (and whether) to test the reliability of expert testimony. No Daubert hearing is categorically required; it becomes appropriate when testimony involves new, complex, or unusual science, or when there is evidence the methodology was skewed or misapplied.
Bullcoming v. New Mexico, 564 U.S. 647 (2011) (n.1). Cited to recognize that gas chromatography is a widely used, well-established technique for quantitative analysis—supporting the circuit court’s decision that no Daubert hearing was necessary for standard GCMS toxicology.
State v. Birdshead, 2015 S.D. 77, 871 N.W.2d 62; State v. Packed, 2007 S.D. 75, 736 N.W.2d 851. These cases reinforce due process principles that defendants must have a meaningful opportunity to present a complete defense—but within the confines of the substantive law and evidentiary rules.

Legal Reasoning

1) Expert disclosure and the exclusion of the defense toxicologist (Urfer).

The circuit court’s order required the parties to disclose witnesses and exhibits by a set deadline. Anderson disclosed the forensic toxicologist and her written report only after the deadline, describing her as a “rebuttal” expert. The Supreme Court held that exclusion was within the court’s discretion because:

The disclosure order was authorized by SDCL 23A‑45‑13 (trial courts may proceed in a lawful manner where procedures are not otherwise prescribed).
Anderson intended to use Urfer in his case-in-chief, not solely to rebut the State after it rested; the “rebuttal witness” label did not insulate him from the disclosure obligation.
Enforcement of disclosure deadlines serves legitimate interests in the criminal process and does not violate the defendant’s right to present witnesses when the sanction is proportionate and grounded in orderly trial administration.

The Court situates this ruling within a familiar abuse-of-discretion and prejudice framework. Anderson did not show a reasonable probability that admitting Urfer would have changed the verdict, particularly given the statutory resolution of the isomer issue and the lab’s established methodology.

2) Limiting the pharmacist expert (Silva) to her proven expertise.

Silva had substantial retail pharmacy experience and was qualified to testify about OTC medications that contain l‑methamphetamine and the existence of methamphetamine isomers. However, the circuit court barred her from testifying about a laboratory “20% margin of error.” The Supreme Court affirmed because:

Expert qualification is domain-specific: a pharmacist’s coursework in statistics does not automatically qualify her to opine on forensic GCMS validation, measurement uncertainty, or lab quality systems.
The meaning of “±20%” at issue was technical and, as explained by the State’s chemists and the lab deputy director, referred to an acceptable quantitation range around a concentration value—not to a percentage chance of misidentifying a controlled substance.
Silva did not demonstrate familiarity with this measurement framework, making her opinion both unqualified and, in the court’s view, unhelpful or potentially confusing.

3) Denying a Daubert hearing on GCMS toxicology.

The Court emphasized trial courts’ latitude under Daubert and Kumho Tire in deciding whether—and how—to assess expert reliability. A hearing is more apt when the science is novel, complex, or susceptible to skewed application. In Anderson:

GCMS is a widely accepted, standard method for toxicology (reinforced by Bullcoming).
The chemists’ qualifications were evident from their CVs; the circuit court found “adequate empirical proof of validity” and saw no indication of improper method application.
Because the challenge focused on familiar techniques without any showing of new theories or deviations, a full Daubert hearing was unnecessary.

4) Fair-trial claim and the “isomer defense.”

Anderson argued his trial was unfair due to limitations on isomer-related evidence and lab reliability arguments. The Supreme Court rejected this for two reasons:

Substantive law eliminates the isomer distinction: SDCL 34‑20B‑16 lists methamphetamine as a Schedule II controlled substance and expressly includes “isomers” and “salts of isomers.” Therefore, l‑methamphetamine is controlled, and the State need not prove which isomer was ingested. Anderson’s proposed jury instruction to the contrary was properly rejected (and the rejection was not appealed).
Meaningful opportunity to present a defense: The trial court allowed Anderson to elicit substantial testimony regarding isomers and to cross-examine the State’s chemist after the State’s witness mentioned l‑methamphetamine’s presence in OTC products. He also called the lab’s deputy director and a pharmacist to explore testing practices and OTC formulations. Within the bounds of applicable law and evidence rules, he received a fair opportunity to present his theory.

Impact and Practice Implications

Substantive drug law: No isomer-based safe harbor. The Court’s statutory reading has immediate, practical consequences: in South Dakota, methamphetamine’s isomers—including l‑methamphetamine—are Schedule II substances. Prosecutors need not establish d‑ versus l‑isomer identity in unauthorized ingestion cases under SDCL 22‑42‑5.1. Defense theories predicated on the legality of l‑methamphetamine will fail as a matter of law.
Forensic toxicology litigation: GCMS challenges. Routine GCMS toxicology—absent a novel theory or evidence of misapplication—will not automatically trigger a Daubert hearing. Defendants aiming to exclude toxicology evidence should (a) develop lab-specific proof of departures from validation or SOPs; (b) identify unusual techniques; or (c) show how application errors “skewed” reliable methods in their case. Generalized critiques or citations to non-binding cases (e.g., Kreps) will have limited traction without a concrete link to the lab’s actual practices in the case at hand.
Measurement uncertainty and how to argue it. The opinion clarifies a common confusion: a laboratory’s “±20%” relates to quantitative uncertainty in concentration, not to the chance of a false identification. Counsel should tailor examinations accordingly. If contesting reliability, consider engaging a qualified forensic toxicologist who can speak to the lab’s method validation, calibration ranges, QC/QA acceptability criteria, and measurement uncertainty in a scientifically accurate way—and disclose that expert on time.
Expert disclosure discipline in criminal cases. Courts can, and will, enforce pretrial disclosure deadlines against the defense. Labeling an expert “rebuttal” will not excuse nondisclosure if the witness is intended for the case-in-chief. Practitioners should expect exclusion as a viable sanction for noncompliance and plan disclosures accordingly.
Fair-trial boundaries. The decision underscores that due process secures a meaningful chance to present a defense, not the right to present legally invalid theories or to circumvent neutral procedural orders. When defendants can cross-examine State experts, call permitted witnesses within their expertise, and present evidence consistent with the governing substantive law, appellate courts are unlikely to find a due process violation.
Jury instructions in isomer cases. The Court’s statutory analysis strongly suggests that jury instructions distinguishing d‑ and l‑isomers as controlled versus not controlled are legally erroneous in South Dakota. Trial courts should avoid such distinctions, and parties should align instruction requests with SDCL 34‑20B‑16’s text.

Complex Concepts Simplified

Isomers (d‑ vs l‑methamphetamine): These are mirror-image forms of the same molecule. Some OTC decongestants have contained l‑methamphetamine derivatives. South Dakota law (SDCL 34‑20B‑16) treats methamphetamine and all its isomers as Schedule II controlled substances. Practically, the State does not need to show which isomer was present to prove unauthorized ingestion.
GCMS (Gas Chromatography Mass Spectrometry): A two-step analytical technique. Gas chromatography separates the components of a sample; mass spectrometry then identifies and quantifies them. It’s a gold-standard method in forensic toxicology and widely accepted by courts.
“±20% margin of error” in lab reports: In this context, it does not mean a 20% chance the lab got it wrong. It reflects the acceptable range around a reported concentration (e.g., 100 ng/mL ±20% means 80–120 ng/mL), derived from method validation and quality controls. Identification and quantitation are different questions; the former asks “what is it?” and the latter asks “how much?”
Daubert hearing: A pretrial proceeding sometimes held to test the reliability and relevance of expert testimony. Courts do not have to hold one in every case—especially where the technique is standard, the expert is qualified, and there is no sign of methodological novelty or misapplication.
Case-in-chief vs. rebuttal evidence: Case-in-chief is the evidence a party presents to meet its burden; rebuttal responds to new evidence raised by the other side. Labeling a witness “rebuttal” does not bypass disclosure requirements if the witness will be used in the case-in-chief.
Unauthorized ingestion (SDCL 22‑42‑5.1) and mens rea: The statute requires proof that the defendant “knowingly” ingested a controlled substance. In this case, the defense did not argue “unknowing” ingestion; instead, it incorrectly claimed that knowingly ingesting l‑methamphetamine is lawful, which the Court rejected.

Conclusion

State v. Anderson delivers a clear and consequential statement on three fronts. First, it removes any lingering doubt that, under South Dakota law, methamphetamine’s isomers—including l‑methamphetamine—are Schedule II substances; the State need not differentiate isomers to prove unauthorized ingestion. Second, it reaffirms robust trial-court discretion to enforce expert disclosure orders in criminal cases and to exclude late-disclosed experts, even when styled as “rebuttal,” if intended for the case-in-chief. Third, it underscores that Daubert hearings are not automatic where experts employ established methods like GCMS and there is no showing of novel science or misapplication.

For prosecutors, the decision streamlines proof in methamphetamine-ingestion cases and reduces the need for isomer-specific testing. For defense counsel, it signals that successful reliability challenges must be tightly connected to the specific lab’s validated methods, QC data, and application in the case—and that experts must be timely disclosed. For trial courts, it confirms that disciplined docket control and judicious limits on expert scope, together with a correct reading of the Schedule II statute, are compatible with a defendant’s due process right to present a defense.

In the broader legal landscape, Anderson functions as both a substantive and procedural precedent: it clarifies the statutory reach of SDCL 34‑20B‑16 and reinforces pragmatic, deferential standards for managing expert evidence in criminal trials—delivering predictability in drug prosecutions and evidentiary practice alike.