South Carolina Bars Penile Plethysmography (PPG) Evidence in SVP Trials Absent Standardized, Reliable Science

Case: In the Matter of the Care and Treatment of Andy Eugene Hyman (S.C. Sup. Ct. Op. No. 28330, filed May 13, 2026)
Posture: Certiorari to the Court of Appeals; Court of Appeals reversed SVP commitment based on admission of PPG evidence; Supreme Court affirmed and remanded for new proceeding.

1. Introduction

This opinion arises from South Carolina’s civil commitment process under the Sexually Violent Predator Act (“SVP Act”), which authorizes the State to seek long-term secure confinement and treatment of qualifying offenders who suffer from a mental abnormality or personality disorder making them “likely to engage in acts of sexual violence if not confined.” The SVP Act places on the State the highest burden of proof—beyond a reasonable doubt.

Respondent Andy Eugene Hyman had prior convictions for criminal sexual conduct with a minor. As required by statute, the South Carolina Office of Mental Health (“OMH”) performed the pre-commitment evaluation and concluded that, although Hyman had pedophilic disorder, he did not meet the SVP statutory threshold because he was not at a heightened risk of reoffending. Dissatisfied, the State sought a “second opinion” from the Medical University of South Carolina (“MUSC”) Sexual Behavior Clinic and Lab, which concluded Hyman was an SVP. The core dispute became whether MUSC’s use of penile plethysmography (“PPG”)—a controversial physiological measure purportedly quantifying sexual arousal to stimuli—could be admitted as scientific evidence.

The trial court admitted PPG evidence; a jury found Hyman to be an SVP. The Court of Appeals reversed, holding the PPG evidence failed reliability requirements under Rule 702 and State v. Council. The Supreme Court granted certiorari due to widespread controversy over PPG’s use in SVP evaluations and to resolve admissibility in South Carolina.

2. Summary of the Opinion

The Supreme Court affirmed the Court of Appeals, held that PPG results are presently not sufficiently reliable to be admissible under Rule 702, SCRE and State v. Council, and further held the evidence is excludable under Rule 403, SCRE due to unfair prejudice and jury confusion. The Court also found the error was not harmless, emphasizing the State’s heavy reliance on the PPG at trial and the jury’s swift verdict (22 minutes). The matter was remanded for a new SVP commitment proceeding.

3. Analysis

3.1 Precedents Cited (and How They Shaped the Result)

A. South Carolina evidentiary framework

• State v. Council (the controlling reliability framework): The Court applied Council’s four-factor reliability inquiry for scientific evidence under Rule 702—(1) publications and peer review; (2) prior application to the type of evidence; (3) quality control procedures; and (4) consistency with recognized scientific laws and procedures. The Court’s detailed factor-by-factor analysis drove the conclusion that PPG fails reliability primarily because of lack of standardization in administration and scoring.
• In re Care & Treatment of Bilton: Used as a South Carolina touchstone recognizing that PPG “is controversial and has been criticized for a lack of standardization and for being subject to manipulation,” and to distinguish Illinois (Frye) treatment of PPG from South Carolina’s reliability-first approach.
• State v. Chavis: Cited to emphasize that “mere procedural consistency does not ensure reliability” without proof the procedures yield reliable results—undercutting MUSC’s argument that its internal controls (temperature, calibration, countermeasures) cure the method’s broader scientific defects.
• State v. Commander, Vaught v. A.O. Hardee & Sons, Inc., and State v. Pagan: These cases supplied standards of review and prejudice principles for evidentiary rulings, anchoring the Court’s conclusion that admitting the PPG was a manifest abuse of discretion and that reversal required probable prejudice.
• In re Care & Treatment of Gonzalez, State v. Byers, and State v. Reeves: Provided the harmless-error framework. The Court used these authorities to determine the PPG’s admission could reasonably have affected the outcome, especially given how the State argued that the PPG results alone were “enough” for commitment.

B. Out-of-state and federal PPG authorities (majority rule and due process concerns)

The opinion aligned South Carolina with the “overwhelming majority” of jurisdictions criticizing PPG’s forensic reliability, citing authorities both within the body of the opinion and in an extensive Appendix. Key citations included:

• United States v. Weber and Rudy-Glanzer ex rel. Doe v. Glanzer: Used to illustrate judicial recognition that plethysmography lacks “uniform administration and scoring guidelines” and that courts have found results inadmissible due to absence of accepted standards, even if the test may assist treatment/monitoring.
• United States v. Powers: Emphasized that scientific literature does not regard PPG as a valid diagnostic tool for forensic purposes due to the lack of accepted standards, while acknowledging treatment utility—mirroring South Carolina’s distinction between therapeutic use and courtroom admissibility.
• Commonwealth v. Ortiz, State v. Spencer, Gentry v. State, and others in the Appendix: Reinforced the central defect—non-standardized stimuli and protocols are “intrinsic to the result produced,” making reliability “inherently dubious” and posing high risk of misleading factfinders.
• State v. Floyd Y.: Not a PPG case per se in the excerpted use, but pivotal to the Court’s Rule 403 analysis—highlighting the heightened risk that jurors will rely on unreliable expert-introduced material in SVP-type proceedings framed as a “battle of the experts,” where accusations are devastating and jury predispositions may amplify prejudice.
• United States v. Medina, United States v. McLaurin, United States v. Rhodes: Bolstered the view that PPG is unusually invasive and that there is no consensus on reliability.
• Berthiaume v. Caron: Cited in the Court’s descriptive framing of PPG as “especially unpleasant and offensive,” reinforcing the Court’s sensitivity to the test’s intrusiveness as part of the Rule 403 unfair-prejudice calculus.

C. Distinguishing minority-admissibility jurisdictions

The Court addressed the few jurisdictions that admit PPG evidence (Washington, Illinois, Florida) and treated them as non-persuasive for South Carolina:

• Washington was distinguished because it “explicitly permits” introduction of PPG results by statute (Wash. Rev. Code Ann. § 71.09.050(1)).
• Illinois and Florida were distinguished because they follow the Frye standard, which does not require the same reliability inquiry South Carolina demands under Rule 702 and State v. Council. The Court cited Frye v. United States to explain the doctrinal difference.

3.2 Legal Reasoning

A. Rule 702 + Council: PPG fails reliability due to non-standardization

The Court did not merely note controversy; it identified a structural problem that “necessarily prevents any finding of reliability”: PPG’s lack of standardization in both (i) test protocols and (ii) result interpretation. Applying the four Council factors:

• Factor 1 (publications/peer review): The literature is polarized; even proponents acknowledge non-standardization. The DSM-5’s recognition that “sensitivity and specificity … may vary from one [laboratory] to another” was treated as an admission of variability inconsistent with courtroom reliability. The Court also found supportive studies less informative because they often omit the stimulus sets used, thwarting replication and comparison.
• Factor 2 (prior application to this context): OMH—the default evaluator in SVP proceedings—refuses to use PPG in pre-commitment evaluations due to reliability/validity concerns. That institutional practice, in the Court’s view, carried “considerable weight” and confirmed that SVP assessments can be performed without PPG.
• Factor 3 (quality control): MUSC’s internal controls (calibration, environmental controls, attention/faking countermeasures) were “admirable” but not shown to be standardized across laboratories nor supported by research proving effectiveness, rendering this factor at best neutral.
• Factor 4 (consistency with recognized scientific practices): This was the decisive failure. The Court emphasized that standardization is foundational to scientific reliability. PPG varies across laboratories in numerous ways (e.g., types of stimuli, sampling rates, instructions, scoring methods). The Court singled out:
  • Cut score arbitrariness: MUSC’s choice of a 5mm threshold (versus literature’s 2.5mm) lacked validation and could be changed at will, illustrating the absence of an external standard or certifying body.
  • Stimuli-set variability and MUSC’s “two tests back-to-back” practice: MUSC’s unusually prolonged, multi-set administration had not been studied for impact and undermined claims that any single set yields reliable results. Further, tailoring stimuli to match prior offenses raised the specter of laboratory-driven variability affecting outcomes.

Synthesizing these factors, the Court announced a categorical, forward-looking rule: PPG results are “generally inadmissible … unless and until the underlying science is more thoroughly developed” and uniform enough to permit a reliability finding.

B. Rule 403: “aura of objectivity” + dubious probative value = unfair prejudice

The Court provided an independent exclusion ground: PPG transforms an intimate, subjective experience into numerical data “cloaked” in scientific authority, creating an “aura of objectivity.” The Court identified two jury-facing dangers:

• Disproportionate persuasive force: PPG results become “particularly powerful” and hard to discount.
• Role displacement: The veneer of science can diminish the factfinder’s responsibility to weigh credibility and resolve competing expert views.

Crucially, those dangers might be tolerable if the science were strong. But because reliability is “dubious,” the probative value is limited and the risks of confusion and unfair prejudice become dominant—triggering exclusion under Rule 403.

C. Harmless error: the State made PPG the centerpiece

The Court’s prejudice analysis was grounded in the actual trial record. It rejected the State’s attempt to minimize PPG as “a single data point,” observing:

• Dr. Gottfried called PPG “the gold standard,” “objective,” and a “strong predictor.”
• The State argued the PPG “proved” current danger when opposing directed verdict.
• Closing argument asserted PPG evidence “in and of itself” justified secure commitment.
• Both experts agreed Hyman’s actuarial scores placed him “squarely within the average rate of recidivism.”
• The jury deliberated only 22 minutes.

On these facts, the Court found a “reasonable probability” that the verdict was influenced by the wrongly admitted evidence and ordered a new proceeding.

3.3 Impact

• Bright-line evidentiary guidance in SVP litigation: Trial courts now have a clear directive that PPG evidence is generally inadmissible in South Carolina “for now,” reducing inconsistent rulings and preventing SVP trials from turning on an unstandardized psychophysiological technique.
• Re-centering SVP proof on validated methods: The decision elevates actuarial tools (e.g., Static-99R/Static-2002R) and clinically grounded assessments that can satisfy Rule 702 reliability standards without relying on PPG.
• Constraining “second opinion” strategy: The Court implicitly criticized the pattern in which OMH performs evaluations without PPG and the State seeks MUSC opinions that “largely” hinge on PPG. Going forward, second-opinion evaluators will need to justify SVP conclusions through admissible, reliable methodologies.
• Broader scientific-evidence jurisprudence: The opinion reinforces South Carolina’s distinctiveness from Frye jurisdictions and signals skepticism toward forensic techniques lacking enforceable standards, external oversight, and reproducibility—especially where evidence carries outsized persuasive weight.
• Jury-protection emphasis: By pairing Rule 702 and Rule 403, the Court highlights that even “scientific-looking” evidence can be excluded when it risks misleading factfinders in high-stakes proceedings with emotionally charged facts.

4. Complex Concepts Simplified

• SVP commitment (civil, but high burden): Although the proceeding is civil, the State must prove SVP status beyond a reasonable doubt, reflecting the severe liberty deprivation of long-term confinement.
• Rule 702, SCRE (scientific expert evidence): Expert scientific testimony is admissible only if it helps the jury, the expert is qualified, and—most importantly here—the underlying science is reliable.
• State v. Council reliability factors: Courts look to peer review, prior use in the relevant context, quality control, and consistency with accepted scientific procedures. A method can fail if it cannot be replicated or compared across settings.
• Reliability vs. validity (as the opinion explains):
  • Reliability: Do repeated tests produce similar results?
  • Validity: Does the test measure what it claims to measure?
  The Court focused on reliability (and the scientific architecture needed to support it), while also recognizing validity concerns.
• Rule 403, SCRE (unfair prejudice): Even relevant evidence can be excluded if it is likely to mislead the jury or provoke a decision on an improper basis. Here, the “scientific” appearance of PPG magnified its prejudicial effect.
• Harmless error: An appellate court will not reverse for an evidentiary mistake if the mistake likely did not affect the result. The Court found the opposite: PPG likely drove the verdict.

5. Conclusion

The Supreme Court of South Carolina adopted the majority rule rejecting PPG as courtroom science in its present state. By holding PPG results generally inadmissible under Rule 702 and State v. Council—and independently excludable under Rule 403—the Court placed reproducibility and standardization at the center of forensic admissibility, particularly in SVP trials where the stakes are exceptional and expert testimony can dominate the factfinding process. The decision not only mandates a new commitment proceeding for Hyman, but also reshapes SVP litigation statewide by removing a highly persuasive yet insufficiently reliable form of “objective” evidence from the jury’s consideration unless and until the science matures into a standardized, verifiable methodology.