CBS News correspondent Tracy Smith discusses the active role that Michelle McNamara, a writer married to the comedian Patton Oswalt, took to investigate the Golden State Killer, and how it may just be the key to solving the 40-year-old case. Learn more about the investigation on an all-new "48 Hours" airing Saturday, April 22 at 10/9c on CBS.Subscribe to the “48 Hours" Channel HERE: http://bit.ly/1DvRWbTWatch Full Episodes Of "48 Hours" HERE: http://bit.ly/1fop6N1Investigate with "48 Hours: Crimesider" HERE: http://cbsn.ws/20pdMsuFollow “48 Hours” on Instagram HERE: http://bit.ly/1OLG2B9Like "48 Hours" on Facebook HERE: http://on.fb.me/1KkQuRnFollow "48 Hours" on Twitter HERE: http://bit.ly/1MOCAXfFollow "48 Hours" on Google+ HERE: http://bit.ly/1HqF6MrListen to “48 Hours” Podcasts HERE: http://bit.ly/1h0fPUgGet the latest news and best in original reporting from CBS News delivered to your inbox. Subscribe to newsletters HERE: http://cbsn.ws/1RqHw7TGet your news on the go! Download CBS News mobile apps HERE: http://cbsn.ws/1Xb1WC8Get new episodes of shows you love across devices the next day, stream local news live, and watch full seasons of CBS fan favorites anytime, anywhere with CBS All Access. Try it free! http://bit.ly/1OQA29B---"48 Hours" investigates the most intriguing crime and justice cases that touch on all areas of the human experience including greed and passion. For 27 seasons, "48 Hours" has developed a rich history of original reporting and impact journalism that has helped exonerate wrongly convicted people, caused cold cases to be reopened and solved, and along the way changed lives. Check local listings for "48 Hours" broadcast times.