I personally think Person of Interest is just barely in the Sci-Fi realm, for being centered around a fictional, near-omniscient automated surveillance network. It also has some themes that overlap with other common Sci-Fi/Fantasy stories, such as vigilante heroes and government conspiracies. Overall though, it seems a bit closer to crime drama (as mentioned on Wiki) than true Sci-Fi.
I'm asking because I have a question about the show which is actually not about any of the Sci-Fi aspects. I can see that there is already one question about the show here - with an accepted answer from myself, no less. However, I thought it might be best to double-check here before making a habit of asking about the series on Sci-Fi instead of Movies & TV.