COMING UP ON 48 HOURS MYSTERY:

UPDATE: TWO KEY WITNESSES STEP FORWARD FOLLOWING 48 HOURS MYSTERY BROADCAST, PLAYING A CRUCIAL ROLE IN SOLVING A COLD CASE

"THE BOY NEXT DOOR" SATURDAY, MARCH 10 (10:00 PM, ET/PT)

WHAT: Three women brutally murdered from Chicago to Los Angeles and an alleged serial killer on the run. How did a 48 HOURS MYSTERY broadcast help catch the "The Boy Next Door?"

WHO: Michael Gargiulo was tracked for almost two decades by police in California and Illinois who suspected him of murdering several young women, but authorities lacked the hard evidence to arrest him. Investigators believed Gargiulo murdered a friend of actor Ashton Kutcher, Ashley Ellerin, and another woman, Maria Bruno, in their California homes. Not until a third woman survived a vicious knife attack would police have the evidence needed to arrest Gargiulo. When California police discovered Gargiulo's DNA sample was already in the national database, another murder was brought to light. The third murder took place nearly two decades earlier, thousands of miles away, in the Chicago suburb of Glenview, Ill. In 1993, Tricia Pacaccio, who had just graduated from high school, was savagely stabbed and left on the side porch of her home where her father, Rick, found her. Unfortunately, evidence recovered at the scene was never enough for Chicago authorities to indict Gargiulo for this crime - until the May 14, 2011 broadcast of 48 HOURS MYSTERY. The broadcast prompted two new witnesses to step forward. In their testimony before a Chicago-based grand jury, they revealed that Gargiulo admitted killing Pacaccio decades earlier. 48 HOURS MYSTERY correspondent Maureen Maher investigated the remarkable connections between cold cases going back almost 20 years, with the detectives and the victims' families and friends who never lost faith that justice would eventually be served.

WHEN: Saturday, March 10 (10:00 PM, ET/PT)

WHY YOU SHOULD WATCH: Currently Gargiulo is facing two murder charges in California for the death of Ellerin and Bruno along with charges of attempted murder and rape of the third woman who survived to tell. And now, because of 48 HOURS' efforts, Gargiulo has been indicted for the murder of Tricia Pacaccio almost 20 years ago in Chicago. Without the 48 HOURS MYSTERY broadcast, the Pacaccio family might never have seen justice served for the 1993 death of Tricia.

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