Marcia Clark on Investigation of Dr. Conrad Murray

ET legal correspondent Marcia Clark is breaking down the investigation of Michael Jackson's former physician, Dr. Conrad Murray.

"The fact that they're executing multiple warrants shows that they're zeroing in on him and slowly, slowly, slowly tightening the net until they finally get enough to either decide they’re going to indict or charge him -- or not," Clark tells ET about the focus on Dr. Murray.

Clark tells ET that the King of Pop's toxicology reports can help determine if any one person is responsible for Jackson's death.