What Do I Do to Investigate a Biased Witness?

What do we do if we have a biased witness? 

Probably most of our witnesses are biased and we need to work around that because that is part of human nature. And we also need to identify it. So, maybe everybody told me that Bob stole the truck on Tuesday, but now one person's not telling me that. Well, let's explore why you might be telling me something different. Do you have some bias about that? Maybe you're Bob's best friend, maybe your Bob's daughter, maybe you hired Bob into the company. As an investigator, just identifying the potential ability of somebody to be bias about a topic is part of what can make your investigative interview with them more fruitful.