St. Paul police have opened an internal affairs investigation into an officer for allegedly knocking a teenager off his minibike as he sped down his block in St. Paul Park.

Officer Ronald Himes, currently assigned to the crime lab, has been with the St. Paul police since 2008. On Thursday, he was one of several personnel who helped lead tours of the department’s revamped forensic services unit.

Mica Franke, who was 15 at the time of the incident in May, said he was testing his minibike after making some repairs in hopes of selling it for $500.

Franke said he was driving about 40 miles per hour when Himes ran at him in the street, stuck out his arm and hit him in the chest.

The blow knocked Franke off the bike, injuring his elbow and hip, he said. Himes’ handprint was imprinted on his chest for three days, he said.

Himes swore at him and wouldn’t let him leave, the teen said. A witness on a motorcycle came to help him and Himes got into an argument with the man, according to a police report. That’s when Franke said he was able to get home and have his father call 911.

Himes wasn’t arrested and no criminal charges were filed against him. When St. Paul Park city attorney Jim Shiely asked the Washington County attorney’s office to look at possible charges, two senior prosecutors reviewed the case and told County Attorney Pete Orput they couldn’t prove the case beyond a reasonable doubt in court. If Himes had been charged, it would have been misdemeanor assault.

Orput said he invited Shiely to take the case to another municipal prosecutor to review. Shiely couldn’t be reached for comment.

Jessica Heroux, Mica’s mother, said she was shocked to find out Himes was a police officer. She said she was disappointed with how St. Paul Park police handled things.

Franke is the nephew of St. Paul Park Mayor Keith Franke.

Attorney Michael Padden served Himes notice Thursday that he is being sued for negligence and defamation for lying about what happened. Himes has no disciplinary action as a police officer.

Last month, Mica Franke was charged with felony first-degree aiding and abetting aggravated robbery with two other teenagers for allegedly taking $250 from an associate.