State v. Kyle Lee Monahan, 913 N.W.2d 894

Single-vehicle crash (Aug 20, 2011) killed passenger R.C.; Kyle Monahan was seriously injured and charged with homicide by intoxicated use of a motor vehicle. The central factual dispute at trial: who was driving when the crash occurred.
R.C. owned a portable GPS unit that recorded timestamped coordinates for the trip from a family farm to the crash; data showed very high speeds (often >100 mph) and a two-minute stop in Shullsburg.
The circuit court admitted only the GPS segment after the two-minute stop and excluded the earlier segment (farm to stop) as improper other-acts evidence; the State later conceded that exclusion was erroneous.
Defense theory: the excluded GPS segment would corroborate eyewitness testimony that R.C. was driving when they left the farm and would support an inference she continued driving (undercutting the State’s proof that Monahan drove at the crash).
Prosecution evidence: multiple pretrial and on-scene admissions by Monahan that he was driving; Trooper Parrott’s crash-reconstruction placing Monahan in the driver’s seat; DNA from Monahan on the driver-side airbag; defense expert Erdtmann testified the physical evidence could not establish driver identity to engineering certainty.
Court of appeals accepted the State’s concession of error as to exclusion but found the error harmless; the Wisconsin Supreme Court affirmed, applying the harmless-error framework and concluding the exclusion did not affect the verdict.

Issue	Plaintiff's Argument (State)	Defendant's Argument (Monahan)	Held
Whether exclusion of GPS data (farm → two-minute stop) was erroneous and, if so, whether the error was harmless	Conceded error in excluding the GPS segment but argued the exclusion was harmless because the State’s case remained strong without it	Exclusion deprived Monahan of material evidence corroborating that R.C. (not Monahan) was driving before and after the stop; exclusion was prejudicial and required reversal	Court assumed the exclusion was erroneous but held the error was harmless beyond a reasonable doubt and affirmed conviction
Proper application of harmless-error factors to evidentiary exclusion	Harmlessness shown by frequency/limited use of the excluded evidence, lack of importance to elements, consistency of State’s evidence, and overall strength of the State’s case	Harmlessness not shown because excluded GPS data was central to defense, uncontradicted by other evidence, and would have directly rebutted prosecutor’s closing argument	Court applied multi-factor harmless-error test (including frequency, importance, corroboration, duplication, nature of defense, nature of State’s case, and overall strength) and found most factors favored the State

State v. Hunt, 360 Wis. 2d 576 (Wis. 2014) (harmless-error standard and burden on the State to show error did not contribute to verdict)
State v. Martin, 343 Wis. 2d 278 (Wis. 2012) (factors to consider in harmless-error analysis)
State v. Norman, 262 Wis. 2d 506 (Wis. 2003) (harmless-error guidance)
State v. Nelson, 355 Wis. 2d 722 (Wis. 2014) (application of harmless-error factors)
Kotteakos v. United States, 328 U.S. 750 (U.S. 1946) (origins and purpose of harmless-error doctrine)
Delaware v. Van Arsdall, 475 U.S. 673 (U.S. 1986) (considering overall strength of the prosecution’s case in harmless-error review)
United States v. Lane, 474 U.S. 438 (U.S. 1986) (errors less likely to affect verdict where evidence of guilt is overwhelming)