The 23-year-old pleaded guilty to molesting his 6-year-old niece when he was 15. Under conditions of the guilty plea, Heimlich, a native of Washington State, was not required to disclose that he was a sex offender, but served two years of probation.
During Heimlich's junior season with Oregon State in 2017, his sex offender status became public due to what was called a clerical error by state police. At the time, Heimlich withdrew from the team's College World Series roster, but returned to competition for his senior season.
Heimlich has since argued his innocence, claiming the guilty plea was in order to quickly dispense with the case for the sake of family relations, according to Kurt Streeter of The New York Times. The girl's mother, who remained anonymous, told The New York Times "there is no way he didn't do it," given the "very specific" testimony her 6-year-old daughter gave.
Heimlich was not selected in the 2017 and 2018 MLB Draft despite being lauded as a first-round talent.
In August, it was reported that Heimlich agreed to a deal with the Lamigo Monkeys of the Chinese Professional League. However, after news surfaced, the league ordered Lamigo to terminate the contract, citing a zero-tolerance policy for players with criminal history.
The left-hander posted a 2.92 ERA over 129 2/3 innings in his senior year with Oregon State.