Last month I wrote about a DA threatening high school students with child porn prosecutions for taking photos of themselves on their cell phones.

Now comes word of another prosecutor abusing his authority in a teen “sexting” case, this time harassing a high school administrator.

The story starts in March 2008: Ting-Yi Oei, an assistant principal in Virginia, is investigating sexting at his school. He confiscates an underwear snap from a student’s cellphone. He can’t identify the person in the photo, so he reports to his principal and closes the investigation.

When he suspends that student for an unrelated offense a couple of weeks later, the student’s mother calls the cops.

Prosecutors investigate, charge him with failure to report child abuse. That charge isn’t going anywhere, because he made a full report to his principal. So they charge him with child pornography. They delay informing him of the charges so they can have him arrested at school on his first day back after summer vacation.

The media run stories, with his photo, saying he’s been arrested for child porn. He’s placed on leave. Television news crews stalk him. Prosecutors press him to resign. He racks up a hundred and fifty thousand dollars in legal bills.

Finally, three weeks ago — even months after his arrest, and nearly a year after Oei first talked to the cops — a judge throws the charges out, finding Oei has broken no laws.