A woman in Oklahoma has pleaded guilty to a lewdness charge after being caught on camera by a local "drone vigilante".
Brian Bates used a drone to film Amanda Zolicoffer during a liaison with a man last August.
Mr Bates says this was the only occasion on which he has used a drone to film such an encounter.
A civil liberties campaigner pointed out that filming with drones could raise privacy concerns.
According to court documents seen by the BBC, Zolicoffer was sentenced to a year in state prison for the misdemeanour.
"I'm sort of known in the Oklahoma City area," Mr Bates told the BBC.
"For the last 20 years I've used a video camera to document street-level and forced prostitution, and human trafficking."
Mr Bates added that on this occasion he felt safer filming the incident via drone and said that it was able to get "very good footage".
Mr Bates runs a website where he publishes videos of alleged sex workers and their clients.
"I am openly referred to as a video vigilante, I don't really shy away from that," he said.
However, Mr Bates also said that he was reluctant to use his drone in many cases because of safety concerns.
In this instance, said Mr Bates, the two individuals were inside a vehicle and the incident occurred away from other members of the public.