Sgt. Jeff Detwiler was arrested Tuesday afternoon. He's been with the Exeter Police Department for at least five years.
Detwiler is accused of having sex with an underage girl and then trying to coerce her not to report the crime.
Tulare County Asstant District Attorney Anthony Fultz said, "Persuading a witness from testifying as well as a misdemeanor of possession of a controlled substance for being in possession of basically a steroid testosterone."
Investigators say the illegal steroid is mostly used for body building.
In a written statement, Exeter police say the investigation into Detwiler has been going on for several months, and that the sergeant, was a role model of sorts to the victim.
"In mid-May of this year, Exeter police administration was made aware that Detwiler may be engaging in conduct of a sexual nature with an underage member of the departments Explorer program. Detwiler was an advisor for the Explorer post and has been with the department for 10 years."
The chief also added they're performing an internal investigation into his sexual relationship with the underage girl.
The Explorer program is run by the police department for kids ages 14 to 20 who are interested in joining law enforcement.
The Tulare County District Attorney's Office believes Sgt. Detwiler and the victim were involved for some time.
Fultz explained, "We believe it was more of a relationship-type of situation, we charged him with one count but we believe it was more of an ongoing relationship."
Sgt. Detwiler lives in Exeter near a school. His neighbors didn't want to talk on camera but say they're shocked that the friendly dad is accused of the crimes.
Fultz added, "Anytime a police officer is involved in something where criminal charges are filed we do take that very seriously because of the position trust because of how much we rely on them for our safety for our protection."