For more than two decades, John Walsh has been hunting the country's most dangerous criminals. At the helm of the show "America's Most Wanted," Walsh has helped put more than 1,000 fugitives -- serial killers, rapists and child abductors -- behind bars.
"I have caught some of the worst of the worst," he said. "We have caught 17 guys off the FBI's 10 Most Wanted [List]."
"Nightline" accompanied Walsh behind the scenes of his show, shooting on location near San Francisco, where he's on the trail of an alleged gangland killer.
The murder of Charles "CJ" Davis has had little media coverage, but Walsh turns cases such as this one into national stories. From Elizabeth Smart to Jaycee Dugard, whose case he first highlighted in 1991 -- just four days after she was abducted.
"I really think it's a miracle that Jaycee Dugard was found after 18 years," Walsh said. "I've been involved in some long-running cases...but for Jaycee Dugard to be found alive and healthy with two children fathered by her abductor, kidnapper, rapist -- a guy with a rap sheet that long that shouldn't have been found on the street, it's a miracle. It's a wonderful, wonderful ending to a really sad story."
Behind Walsh's anti-crime activism is his own tragic story -- one without the "wonderful" ending.
In July 1981, his 6-year-old son Adam was abducted from a shopping mall in Florida. John and his wife Reve desperately searched for Adam, but their worst fears were realized when Adam's severed head was found in a canal two weeks later. The rest of his body was never recovered.
"I'll always be the parent of a murdered child," Walsh told "Nightline." "Adam will always be in my mind. Your heart is broken. It doesn't matter if it was six months ago or 27 years ago. Your heart is broken. People deal with it differently. Some descend into hell in different ways and you live in that hell."
Adam's murder became one of the most infamous crimes against a child in America. And Walsh used his son's death to raise awareness for missing children across the country, creating the National Center of Missing and Exploited Children. He became a public face of the missing children movement. FOX asked Walsh to host "America's Most Wanted" in 1988, a program that prominently features cases in which children are harmed or missing.
To critics who label him a "fear mongerer," Walsh said that he considers his job "an obligation."
"I believe that knowledge is power. I truly believe that people watch too much TV and think there is going to be that superhero who is going to come in and stop this and that it can't happen to you," Walsh said. "If you spent one day with me, and saw how average crimes affect people in the United States. ...I don't believe in paranoia, I don't believe in fear mongering, I believe we have an obligation to tell our kids that someone might hurt them someday."
"America's Most Wanted" featured Dugard's case three times -- even though many people had given up hope of her ever being found.
When Dugard, now 29, was found living in the backyard of her alleged abductor, Phillip Garrido, Walsh couldn't believe that the 58-year-old had been able to evade authorities time and time again.
Garrido was convicted of kidnapping and repeatedly raping Katie Hall in a Nevada storage unit in 1977 and served more than 10 years of a 50-year sentence before he was paroled. He is also considered a suspect in two other missing child cases, the 1988 abduction of 9-year-old Michaela Garecht and the 1989 disappearance of 11-year-old Ilene Misheloff.
"[Garrido's] a guy that should've never been out there, that's the guy we need to track. That's the level-three violent sex offender that everybody needs to know is next door," Walsh said. "It's not about civil liberties. I grew up in the '60s. I believe in civil liberties, and I believe in America. But I believe that once somebody demonstrated that they're an animal, that they've crossed that line, that they've hurt a woman or a child, then you need to track them."
On the set of his show, Walsh often invites victims' family members to the taping. When he meets parents who have lost their child, he said the pain of losing Adam hits him again.
"I look at this woman and see the pain and the tears in her eyes and say, 'I know where she is at.' She says, 'How could this happen to me? How could I be in this place?' And you really don't have the answer, I still don't have the answer," Walsh said. "I am still heartbroken…and you're wounded, but you will survive. You will go on; you go on and do the best you can to deal with it."
Walsh bonds with the families -- but none more so than the Smart family from Salt Lake City. When their 14-year-old daughter, Elizabeth, was abducted from her bedroom in 2002, Walsh did six shows on her case.
Nine months after Elizabeth Smart was abducted, an elderly couple, who had heard about the smart case on "America's Most Wanted," spotted a man traveling with two companions -- and one of them was a disguised Elizabeth Smart.
"I think the highlight of the 23 years is when the Smart family asked me to fly to Salt Lake City the day that Elizabeth was recovered because we never gave up and Ed and Lois never gave up," Walsh told "Nightline."
"And when I saw Elizabeth walk down the stairs that night, I said, 'This is good, this is a home run.'"
Just last month, Elizabeth Smart, who is now 21, came face to face with her alleged abductor, Brian David Mitchell, in court.
Speaking for the first time, Smart testified that she was raped "on a daily basis up to three or four times," while in captivity for nine months. She testified as part of the proceedings to determine Mitchell's mental competency, in the hope that he can stand trial and that justice will finally be served.
Justice is what had also eluded the Walsh family for decades. But last year, Chad Wagner, a new chief of police in Hollywood, Fla., closed Adam's case, officially declaring that Ottis Toole, a convicted pedophile and serial killer, murdered Adam in 1981. It was an emotional moment for Walsh and his family.
"For 27 years, we have been asking who could take a 6-year-old boy and murder him and decapitate him. Who? We needed to know. We needed to know. And today we know," Walsh said at a news conference.
Walsh told "Nightline" that by declaring Toole the murderer, "justice was served."
"I believe that I knew that Ottis Toole killed Adam before he died. He died eight years before they closed the case. But for Reve and I, and our family, it was the end of that chapter: it was finality," Walsh said. "Not closure, that's a bad word, you never get closure. It's that finality, it's that person that did that horrible thing to you is where they should be. Justice was served. I think that is all that average, good people ask for."
Walsh said that Reve and their three living children -- born after Adam's murder -- have "absolutely" suffered because of his devotion to Adam's case.
"I have spent most of the time of our daughters Megan and Callahan and Hayden, a big portion of their lives on the road. But they have come with me all over the world. They come on location, they have seen what their mother and I are trying to do, to change laws," he said. "I only go after these guys after they have destroyed somebody's lives. I believe in the proactive. If you change the laws, everybody benefits, if you change society's perception about the violence in this country and you make effective social change and be proactive, educate people."
Proactive for Walsh meant lobbying for the Adam Walsh Child Protection and Safety Act, which was signed by President Bush in 2006. The law was intended to create a national registry for the most dangerous sex offenders, like Philip Garrido.
But thus far, states haven't cooperated. Critics say the law is unfair to minors, who are often labeled as sex offenders on the registry for the rest of their lives.
"The Act says that only if you physically or violently offended someone and you're a repeat offender, you should be on the registry forever. I don't believe that every teen offender should be on the registry…I don't believe that a kid who makes one mistake when he's 13 years old and might have exposed himself to somebody, that is not the intention of the Adam Walsh Act," Walsh said. "The Justice Department says there are 100,000 level-three sex offenders who are in violation of their parole or probation...they have disappeared somewhere in America or somewhere in the world. I think that is a serious problem."
With more than 1,000 criminals behind bars since "America's Most Wanted" began, in the end, it always comes back to one case -- that of the son he lost over 28 years ago.
"Walk in my shoes back to July 27th, 1981. Think about it. You waited your whole life for this little boy. You kiss him goodbye one morning and you never see him again. And then you find out two weeks later that someone decapitated him. Just walk in my shoes one day," Walsh said.
Walsh said he hopes his son would be proud of his work today.
"I think wherever he is, he is [proud]. He would be a 35-year-old man," Walsh said. "I don't know, I hope so. I loved that little boy."