Identity thieves are usually after your money, but the consequences of a wrong identity can go much further -to prison or severe medical problems. A list of mistaken identity cases gives an overview of how many ways things could go wrong. Your passport is used to label you a terrorist. A mother is accused of drug abuse because a baby tested positive. A man goes to jail for a crime committed in a country he’s never been to. And there are several ways even DNA tests can identify the wrong person. For example:
Police investigating one particular sexual assault case must have thought the case was going well. They had a semen sample with useable DNA, and it matched DNA of an Alaskan man already in the system. There was just one hitch: The man in question had been in jail when the crime was committed. Was it a mix-up in the system? No, although that's what technicians thought at first. In truth, the solution was even stranger: One year earlier, the jailed man had received bone marrow from the actual assailant, his brother [sources: Aldhous, BBC].
Today, bone marrow recipients sometimes retain some of their own marrow and end up with mixed genetic profiles. But in this case, the jailed man had lost all of his original marrow, and so he registered as a full match for the criminal in question [sources: Aldhous, BBC].
Read about all ten cases of mistaken identity at How Stuff Works.