United States v. William Tyson, 947 F.3d 139

Tyson contacted a 17-year-old via Facebook, arranged prostitution, and transported her across state lines; agents recovered video evidence of sexual activity.
He was indicted under 18 U.S.C. § 2423(a) (transporting a minor for prostitution) and 18 U.S.C. § 2251(a) (using a minor to produce child pornography).
The government moved in limine to exclude any "mistake-of-age" evidence; the district court granted the motion under Fed. R. Evid. 403 as the statutes do not require knowledge of age.
Tyson entered a conditional plea preserving his right to appeal the evidentiary ruling; the district court sentenced him to concurrent 180-month terms.
On appeal Tyson argued (1) knowledge of the victim’s age is an element of both statutes, and (2) the court should read an affirmative mistake-of-age defense into the statutes (including on First Amendment grounds).
The Third Circuit affirmed, holding that neither § 2423(a) nor § 2251(a) requires knowledge of age and that no constitutional or statutory affirmative defense compels admitting mistake-of-age evidence.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether knowledge of the victim's age is an element of § 2423(a)	Tyson: Government must prove defendant knew victim was under 18	Government: "Knowingly" applies to transportation, not victim's age; age is an aggravator	Knowledge of age is not an element; mistake of age is not a defense under § 2423(a)
Whether mistake-of-age evidence is admissible under § 2423(a)	Tyson: Evidence/defense should be allowed (cites state law and precedent)	Government: Evidence irrelevant and prejudicial; Congress omitted scienter on age intentionally	Exclusion affirmed under Rule 403; evidence irrelevant and likely misleading
Whether knowledge of the victim's age is an element of § 2251(a)	Tyson: Circuit split; must prove knowledge or provide defense to avoid chilling speech	Government: Congress removed "knowingly" from age element to facilitate enforcement; scienter not required	Knowledge of age is not an element of § 2251(a); mistake of age not a defense
Whether First Amendment requires an affirmative mistake-of-age defense for § 2251(a)	Tyson: Cites Ninth Circuit (Kantor)—strict liability chills protected speech, so a defense is required	Government: Protecting children is compelling; risk to speech is minimal and outweighed by interests	Court declines to adopt Kantor; no constitutional mandate for a mistake-of-age defense

Flores-Figueroa v. United States, 556 U.S. 646 (presumption that "knowingly" applies to all elements, but contextual exceptions exist)
United States v. X-Citement Video, 513 U.S. 64 (producers may be convicted under § 2251(a) without proof of knowledge of age)
United States v. Hamilton, 456 F.2d 171 (3d Cir.) (statute predecessor did not require knowledge of victim's age)
New York v. Ferber, 458 U.S. 747 (1982) (government has greater leeway regulating child pornography; protecting children is compelling)
United States v. Kantor, 858 F.2d 534 (9th Cir.) (recognized a First Amendment–based mistake-of-age defense for non-obscene material; not followed by other circuits)