From Wikipedia (Taken from PA code):
Corruption of minors. (a) Offense defined.-- (1) Whoever, being of the age of 18 years and upwards, by any act corrupts or tends to corrupt the morals of any minor less than 18 years of age, or who aids, abets, entices or encourages any such minor in the commission of any crime, or who knowingly assists or encourages such minor in violating his or her parole or any order of court, commits a misdemeanor of the first degree.
This charge typically is used only in plead agreements, but not in cases that actually led to a conviction. In the case cited, "coercion by authority" was in play, this was offered to avoid a **** charge. This insinuates that the commonwealth believes that premarital sex is a corruption of morals.
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Sounds kinda weak to me. Why make 16 years the age of consent if you can still charge adults for sleeping with them?