A former dance and gymnastics coach charged with allegedly raping a teenage girl in Jefferson County has pleaded guilty to federal charges for engaging in sexual activity with two girls. The girls were younger than 14, the U.S. District Attorney’s Office reported.
Marco Anton Zomphier, 32, of St. Louis on Sept. 2 pleaded guilty to two counts of coercion and enticement of a minor in the U.S. District Court for the Eastern District of Missouri. He is scheduled to be sentenced on Dec. 2, court documents show.
The prosecuting attorney is recommending a 25-year prison sentence, the U.S. Attorney’s Office said in a statement.
Jefferson County Sheriff’s Office deputies arrested Zomphier in 2024 after one of the victims reported that the former coach started abusing her in 2022. The Jefferson County Prosecuting Attorney’s Office in December 2024 charged Zomphier with first-degree statutory rape or attempted statutory rape of someone younger than 14, statutory sodomy or attempted statutory sodomy of someone younger than 14, first-degree rape or attempted rape and two counts of first-degree rape or attempted rape, according to court records.
After Zomphier was charged in Jefferson County, another victim reported that he abused her in 2013 in St. Louis County. The St. Louis County Prosecuting Attorney’s Office in June 2025 charged Zomphier with two counts of first-degree statutory sodomy and sexual contact with a student by a teacher, according to court documents.
Zomphier is scheduled to appear in Jefferson County Court on Nov. 10, court records show. The case against Zomphier in St. Louis County no longer appears in court records.
According to the guilty plea filed in federal court, Zomphier met the first victim in 2012 when he was her coach at a St. Louis County YMCA. The two exchanged text messages and communicated on two different internet communication platforms.
In 2013, Zomphier began having inappropriate contact with the girl at the YMCA, and he convinced the girl to let him go to her home. At the house, he molested the girl and unsuccessfully attempted to force her to have sex, the plea agreement said.
The relationship between Zomphier and the girl ended in May 2013, which is the same year he stopped working at the YMCA and began working at Pride Gymnastics in Collinsville, Ill., according to the guilty plea.
In the probable-cause statement filed by the Jefferson County Sheriff’s Office in September 2024, the other victim said Zomphier was her cheer coach, and he sent her inappropriate messages through Snapchat.
The girl said starting in April 2022, Zomphier would drive to either her home or school to pick her up. She said on at least three occasions, he drove to either the Target department store or Schnucks grocery store in Arnold and allegedly raped her in the car, the report said.
The girls said the first incident ended because Zomphier’s wife called him, and she said there was a baby in the car during one of the other incidents, according to the report.
The girl told investigators she felt she could not say no to Zomphier because he threatened to post sexually explicit photos and videos of her online and that he would shoot himself outside her window if she told anyone about the incidents, the report said.
According to the guilty plea, the girl’s mother found out about Zomphier’s relationship with her daughter in September 2022, and she banned Zomphier from contacting her daughter but did not report him to authorities. The mother later found out Zomphier was still contacting her daughter, and she complained to Pride Gym and Zomphier was fired.
In February 2023, another parent told the girl’s mother about more incidents of sexual abuse involving Zomphier than she previously told her mom. In May 2023, Zomphier’s wife told the girl’s mother that her husband admitted to the abuse, leading to the Sheriff’s Office findings and arrest of Zomphier, according to the guilty plea.
The Sheriff’s Office, St. Louis County Police, Bethalto Police and FBI investigated the case. Assistant U.S. Attorney Michael Hayes is prosecuting the case.
This case was brought as part of Project Safe Childhood, a nationwide initiative to combat the growing epidemic of child sexual exploitation and abuse launched in May 2006 by the Department of Justice. Led by U.S. Attorneys' Offices and the Criminal Division's Child Exploitation and Obscenity Section, Project Safe Childhood marshals federal, state, and local resources to better locate, apprehend and prosecute individuals who exploit children via the Internet, as well as to identify and rescue victims. For more information, visit justice.gov/psc.