Why is the Benton, Kentucky area so murdery, by episodes?

Benton is a small town in Marshall County, western Kentucky, just outside Paducah. It was founded in 1842, incorporated in 1845, and named after a senator from Missouri, not a Kentucky one. In 1908 Benton and the whole of Marshall County became sundown towns. The Benton area takes in three towns: Benton itself, Paducah 22 miles away and Tiline 23 miles off.

Three episodes cover the four murders on four dates across six years, all in the 2000s: 2002 in Paducah, 2004 and 2008 in Tiline, 2007 in Benton. Episode 158 takes two of the four, its two cases four years apart, while episodes 430 and 520 have one each.