State v. Souther, 169 A.3d 927

On April 12, 2016 Trooper Stevens stopped Samantha Souther after observing erratic driving and signs of intoxication (odor, glassy eyes, slurred speech) and found an open 16‑ounce beer in her car; field sobriety tests indicated impairment and she was arrested for OUI under 29‑A M.R.S. § 2411(1‑A)(A).
The criminal complaint charged only the impairment prong of the statute, not the per se 0.08% alcohol level prong.
Souther sought to admit expert testimony (using the Widmark formula) estimating that a 115‑lb woman who drank one 16‑oz beer (~5% ABV) would have a peak BAC of about 0.05% at the time of driving, and offered a stipulation and a requested jury instruction tied to that estimate.
The court excluded the Widmark‑based testimony under M.R. Evid. 403, explaining the case was about impairment (not excess BAC), the jury would have no objective benchmark, and the numerical estimate risked confusing or prejudicing the jury.
Souther argued 29‑A M.R.S. § 2432(1) (prima facie evidence of non‑impairment at ≤0.05%) made the estimate relevant; the court and appellate majority held the statute’s procedural effect requires a contemporaneous scientific test result and thus did not supply the missing link.
The jury convicted Souther of OUI; the court imposed a fine and license suspension. Souther appealed, challenging exclusion of the Widmark testimony.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Admissibility of expert Widmark estimate of peak BAC in an impairment‑only OUI case	Souther: Widmark estimate showing peak BAC ≈ 0.05% is relevant to impairment and, under § 2432(1), would support a prima facie non‑impairment inference and a jury instruction	State: No scientific BAC test existed; giving a numerical BAC would confuse the jury in an impairment case and risk prejudice; § 2432 procedural effect requires a contemporaneous test	Court affirmed exclusion under M.R. Evid. 403: Souther’s offer lacked the necessary nexus showing how the estimated BAC related to actual impairment, and § 2432 applies only when a scientific test result is introduced

State v. Tibbetts, 604 A.2d 20 (Me. 1992) (upheld admission of Widmark expert where BAC at the relevant time was central and there was a later breath test to anchor the estimate)
State v. Grigsby, 666 A.2d 503 (Me. 1995) (upheld exclusion of Widmark testimony when no scientific test existed and the proffer failed to link estimated BAC to impairment)
State v. Richford, 519 A.2d 193 (Me. 1986) (relevance objection sustained where Widmark proffer lacked information tying estimated BAC to degree of impairment)
State v. Atkins, 129 A.3d 952 (Me. 2015) (defining "under the influence" as any impairment of physical or mental faculties)