How Do You Stop Child Porn Before It Starts?

A star in the hit Fox show 'Glee' was arrested on the suspicion of possessing child pornography. How does law enforcement identify and apprehend suspects with child porn? Is there anyway to stop it before the addiction starts?

To watch the panel discussion: http://live.huffingtonpost.com/r/segment/fighting-child-pornography-/5679503a6f753acf01000961