I seem to spend half my life writing about ‘song-theft cases’ – where one artist accuses another of ripping off one of their songs – and when those lawsuits end up in certain US courts we have to talk about the “extrinsic test”. So what the hell is that? Well, I thought the latest filing in the Mariah Carey song-theft case had a decent description of it, so I quoted it pretty much verbatim in my CMU report on that story. And now you have ‘All I Want For Christmas Is You’ in your head and it’s only September! Anyway, here’s the story.