St. John v. Peterson, 2011 SD 58

St. John sued Dr. Peterson for malpractice after a hysterectomy allegedly caused a vesicovaginal fistula.
Post-hysterectomy fistula diagnosed May 24, 2006; initial repair attempts (Latzko procedure and vaginal stitches) failed.
Dr. Peterson attempted multiple repairs June–July 2006; fistula ultimately repaired by another physician.
The trial court severed four related cases to avoid prejudice and later barred evidence of other lawsuits.
On appeal, St. John challenged the trial court’s exclusion of evidence regarding Dr. Peterson’s prior similar cases and related testimony.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the trial court abused its discretion in excluding evidence of prior similar cases.	St. John argues exclusion denied relevant, probative impeachment evidence.	Peterson contends such evidence is prejudicial and not sufficiently probative.	Yes; remand for proper Rule 403 balancing and relevance assessment.

Supreme Pork, Inc. v. Master Blaster, Inc., 764 N.W.2d 474 (S.D. 2009) (relevance and admissibility separate; Rule 403 balancing required)
Kostel v. Schwartz, 756 N.W.2d 363 (S.D. 2008) (abuse of discretion standard; balancing errors potential prejudicial impact)
Mousseau v. Schwartz, 756 N.W.2d 345 (S.D. 2008) (evidentiary ruling presumed correct absent clear abuse)
Novak v. McEldowney, 655 N.W.2d 909 (S.D. 2002) (Rule 403 prejudice vs. probative value; burden on objecting party)
Kaiser v. Univ. Physicians Clinic, 724 N.W.2d 186 (S.D. 2006) (abuse of discretion standard and evidentiary balancing)
State v. Smith, 599 N.W.2d 344 (S.D. 1999) (concepts of relevance and admissibility intertwined)