In June, an assailant with previous drug offense purchased a gun and killed nine worshippers at a church in South Carolina. In traditional gun market, felons can get a gun without background checks from private sellers. Most states require only licensed dealers to conduct background checks but not private individuals.However, background checks are required wherever people buy a smart gun, an effective way to avoid felon’s ownership of a gun. Authorization is a key process during the smart gun purchase. Recording biometric data is a prerequisite to own the gun, and thus it prevents convicted felons from getting access. Even if they steal a smart gun or grab law enforcement officers’ firearms during a struggle, they cannot shoot because their biometric data does not match with that of the guns’ at all. Statistically, it is not rare that police officers are killed by felons who take over their weapons. According to the FBI website, in 2011 alone, nearly 13% of law enforcement officers either were killed by felons with their own weapons or had their weapons