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Jeff is a random character in Grand Theft Auto IV encountered in northern Algonquin, near North Holland.

Niko encounters the erratically-behaving man standing across the street from his apartment, ranting and raving about how he suspects his wife of infidelity. Jeff asks Niko to follow his wife and her male friend and to take pictures of them so he can confirm her treachery. Niko does so, but in the course of which overhears his exasperated wife complaining about how her husband doesn't trust her to have purely platonic male friends, and so Niko mentions to the increasingly erratic Jeff that he doesn't think the picture necessarily proves her guilt.