An interview on Eurogamer talks with Martin Edmonson of Ubisoft Reflections about Driver: San Francisco, the new installment in the action/driving series. He addresses some of the criticisms of the game, including the way the unhinged Tanner is depicted:

Most people that play the game think the actual function of Shift is good fun and bringing something different. There are reviews that get the story, they understand it, they see how Shift came and how it develops. They also recognise that we're showing Tanner's schizophrenia deliberately. One minute he's doing a police investigation and the next minute doing something completely crazy with a bunch of Japanese street racers or a learner driver.

And this is by design - it's an intentional thing. One or two of the reviews just go, "Oh this story is completely ludicrous." You need to stop for a minute and think why have we done it this way. This is why: because he thinks he's having a mental breakdown. I don't think they've thought about it carefully enough. What we have done is, very deliberately, treat it with a light touch. Jones, for example, his partner, is constantly taking the piss out of him. And this is because it's such a ludicrous situation. All the time we're being very, very deliberate about this. Tanner has to basically convince Jones, and he starts to think very quickly that things are not quite as they seem.