San Francisco District Attorney Kamala Harris is a veteran prosecutor who knows the rules of the game. She is now a manager but she was a top flight trial attorney before being elected to her current post. As a San Francisco Criminal Attorney she knows it is her sworn duty to turn over appropiate criminal records of witnesses to defense attorneys.
This is an estabalished law that a first year deputy district attorney will know about. Prosecutors must research the past criminal records of witnesses that they will present at a preliminary hearing or jury trial. When that witness has a past conviction for a felony or a misdemeanor conviction of moral turpitude the prosecutor must turn that information over to the defense.
For prosecutors, most of their witnesses will be police officers. Police officers, just like anyone else, can get in trouble with the law. If the officer has a past criminal record of a felony or crime of moral turpitude, that must be given to the defense attorney. This is what Ms. Harris has failed to do and this is serious. If she deliberately did this she should lose her job and her bar card. If it was negligent then she is incompetent. Either way she obstructed justice.