"James Earl Ray is seen facing the wall at Shelby County Jail. . . . (Photo by Gil Michael/Shelby County Sheriff's Office)"
This image of Ray is one of many photographs and other documents recently discovered in the Shelby County archives and released today, online. See them all here: http://register.shelby.tn.us/media/mlk/
I have never seen a backwards-facing mug shot before. My first impression was that Ray had posed himself that way, a vain act of defiance against his captors. In the Commercial Appeal, reporter Marc Perrusquia asserts that "Dr. Martin Luther King Jr.'s assassin stood face first against the wall, helplessly shoved into a corner by his captors at the Shelby County Jail."
http://www.commercialappeal.com/news/2011/mar/30/window-on-history/
Perrusquia offers no direct evidence for his statement, but he did interview both the photographer, Gil Michael, and the then-sheriff, Bill Morris, so one or both of them may have explained the provenance of the stance.
In either event, it is a potent image.