A 32-year-old former dance and gymnastics coach from St. Louis pleaded guilty this week to two federal counts of coercion and enticement of a minor, admitting he engaged in sexual activity with two girls younger than 14 whom he coached over nearly a decade. Marco Anton Zomphier entered his plea on Wednesday before U.S. District Judge Cristian M. Stevens in Courtroom 10S at the Thomas F. Eagleton U.S. Courthouse in St. Louis, under federal docket number 4:25-cr-00389.
A Coaching Career That Spanned Two States
According to The Leader, Zomphier met the first victim in 2012 at a St. Louis County YMCA, where he began inappropriate contact with her in 2013 before molesting her at her home that same year. He stopped working at the YMCA in 2013 and began working at Pride Gymnastics in Collinsville, Illinois that same year, where the paper reports he later coached a second victim, who said Zomphier was her cheer coach. The relationship with the first victim reportedly ended in May 2013 after Zomphier's wife called him, cutting the encounter short, and the two continued exchanging text messages and communications on two internet platforms afterward.
The Leader's reporting indicates the first victim's mother banned Zomphier from contacting her daughter and complained to Pride Gym about him, which fired him. But the mother reportedly learned in September 2022 that Zomphier had continued contacting her daughter, and did not report him to authorities at that time. She learned more in February 2023, when another parent told her about additional sexual abuse incidents, and Zomphier's wife reportedly told her in May 2023 that Zomphier had admitted to the abuse.
A Second Victim, and Escalating Threats
The second victim reported that Zomphier began abusing her in 2022 and, starting in April of that year, drove to her home or school. Per the same reporting, he sent her inappropriate messages through Snapchat and, on at least three occasions, drove her to a Target or Schnucks in Arnold, Missouri, where she reported he raped her in his car. The Leader's account notes that during one other alleged incident, a baby was in the car. Zomphier is also reported to have threatened to post sexually explicit photos and videos of the second victim online, and threatened to shoot himself outside her window if she told anyone.
A third victim reported that Zomphier abused her in 2013 in St. Louis County. Investigations into the case were carried out by Jefferson County Sheriff's Office deputies, Bethalto police, St. Louis County police, and the FBI. Jefferson County Sheriff's Office deputies arrested Zomphier in 2024.
State Charges Preceded the Federal Case
The Jefferson County Prosecuting Attorney's Office charged Zomphier in December 2024 with multiple counts including statutory rape, attempted statutory rape, statutory sodomy, attempted statutory sodomy and first-degree rape. Under Missouri Revised Statutes § 566.032, first-degree statutory rape of a child under 14 is classified as a Class A felony punishable by five years to life in prison, according to Missouri legal guidance, with mandatory minimums increasing to 10 years under specific aggravating factors.
In June 2025, the St. Louis County Prosecuting Attorney's Office separately charged Zomphier with two counts of first-degree statutory sodomy and sexual contact with a student by a teacher. That St. Louis County case is no longer present in court records, though the pending Jefferson County charges remain active — Zomphier is scheduled to appear in Jefferson County court on November 10, 2026.
Federal Prosecution and Sentencing Ahead
The federal case is being prosecuted by Assistant U.S. Attorney Michael Hayes under Project Safe Childhood, a Department of Justice initiative launched in May 2006 that uses federal, state and local resources to locate, apprehend and prosecute people who exploit children online, according to the U.S. Department of Justice. The initiative is aimed at combating child sexual exploitation and abuse and identifying and rescuing victims. Under 18 U.S.C. § 2422(b), coercion and enticement of a minor carries a mandatory minimum sentence of 10 years in federal prison and a maximum of life imprisonment, per the Cornell Law School Legal Information Institute.
As part of the plea agreement, prosecutors have recommended a 25-year prison sentence to be followed by lifetime supervised release and mandatory sex offender registration upon release, per the U.S. Attorney's Office. Because there is no parole in the federal system, defendants generally serve the vast majority of their imposed sentence. Zomphier is scheduled to be sentenced on December 2, 2026.
Legal representation for the victims said the guilty plea brought a long-awaited sense of validation to the young victims and their families after years of waiting, according to Fox 2 St. Louis. Victims and family members attended the change-of-plea proceedings in federal court.
Broader Federal Scrutiny of Youth Sports Coaches
The case adds to a pattern of severe federal sentences for coaches who abuse young athletes in the Eastern District of Missouri. In a separate case, a former St. Charles County youth sports coach convicted of federal child sexual abuse charges was sentenced by U.S. District Judge Sarah E. Pitlyk to 75 years in federal prison, according to a report shared by Downstate IL Scanner.
The U.S. Center for SafeSport's Minor Athlete Abuse Prevention Policies require participating youth sports programs to mandate immediate reporting of suspected abuse and strictly limit unmonitored one-on-one adult-minor interactions. Missouri Revised Statute § 210.115 also requires individuals with responsibility for the care or supervision of children to immediately report known or suspected child abuse to the Missouri Department of Social Services Children's Division. It remains an open question how the pending state charges against Zomphier in Jefferson County will be resolved following his federal sentencing.
