Why so many uncleared homicides?

Bridget Johnson at PJM has an article looking at the Adam Walsh case and the number of uncleared homicides in the US:

Earlier this month, an Associated Press probe of FBI figures revealed that, despite technological advances in criminalistics, it’s just easier to get away with murder nowadays. The clearance rate of homicides, or cases solved in a year, stood at 61 percent nationwide in 2007, a steady slip over the decades from the first year of modern record-keeping, 1963, when the clearance rate was 91 percent.

In addition to DNA and other scientific advances that should be helping catch more criminals, not fewer, law enforcement also now has the benefit of reaping tips and captures with the help of modern media. America’s Most Wanted, the longest-running show on the Fox network, boasts 1,049 criminals caught with the program’s help as of this writing — yet for 27 years, host John Walsh has been at the center of one of America’s most infamous unsolved mysteries.

I remember when we talked with Bill Bass, forensic anthropologist and author of Death's Acre, he mentioned that due to all of the CSI type shows, people think that it is easier to catch criminals these days when indeed it is not. Part of the problem, he said (and I am recalling this from memory) is that since many of us are strangers and there is less community cohesiveness, no witnesses will come forward when there is a murder or they are reluctant to talk to the police.