Let's say a female investigative journalist is looking into a story where the actors involved clearly know things she doesn't, but much to her frustration, they simple wont talk.
Most of them are men, and after much fruitless effort, she gets an idea. She goes up to one of the men she's trying to get information from and makes him a vary simple proposal: if he'll give her what she wants, and can more or less prove it's legitimacy; then she'll sleep with him, and let him do whatever he wants to her.
After a bit of thought and glancing at her, he agrees. He gives her the information, then she strips down and promptly lets him get to work on her. The next morning however, while she's driving home, feeling nice and clever about herself, she gets pulled over by a cop, and before she knows it, suddenly finds herself in a courtroom, on trial for prostitution.
In Canada and the USA and ... let's say for fun, Japan too; would this be considered prostitution? If not, why? And if so, could the defence use the fact that she did it as part of her journalism job as part of his defence of her?