A teenager in Virginia is facing four months in jail and a lifetime on a sex offender's list for texting videos of his erect penis to his girlfriend.

The 17-year-old from the Washington suburb of Manassas is accused by police of "manufacturing and distributing child pornography" - even if it is so-called 'selfie' porn.

The youth, due to appear 1 August in youth court, had "repeatedly" been told to stop sending "pornographic videos" to the 15-year-old girl, said Manassas City Police in a statement.

The "sexting" case took a surreal twist when police obtained a warrant to photograph the boy's penis to prove that it was the same one that appeared in the text videos.

On Thursday, as publicity about the case grew in the Washington area, they said they would not serve the warrant, which would have involved a drug-induced erection at a local hospital.

Under Virginia law, anyone in possession of obscene photos of a juvenile is technically in possession of child pornography, even if it is a picture of themselves, Foster said.

"It's a very far-reaching law," she said.

In an editorial this week, the Washington Post newspaper, citing an academic study, said the youth's behaviour "puts him in the company of nearly 30% of his peers."