Since the advent of DNA testing in the 1980's, US courts have come to recognize that wrongful convictions are all too common. Some 1600 supposed criminals have been found innocent after all. Now, prosecutorial offices around the country have been opening Wrongful Conviction Units. The latest is the biggest of all — the Los Angeles County District Attorney's Office — which prosecuted 71,000 felony defendants last year. Jackie Lacey is the District Attorney.