That bike looks to be a dual purpose 650. They can be ridden short distances on the highway but those knobby tires will beat you to death.
Here is a link to Kerns' father's obit.
Obituary for John Henry Kerns at Thompson Funeral Home
TS was 44. BF was 20. JK was 49. I kind of agree with Reader, that this was for her mother's check. TS may have been strung out, (she looks strung out in the mugshot), and neglected her mother, and she died. Daughter and her young boyfriend, didn't want to lose that check, so, they hide the body, then try to completely do away with her body. My guess is, that BF was hanging around for the check, and free drugs, from TS. How the other female, that was found nearby, comes into play, idk, but, I've got a couple theories, however, I'm keeping them close to vest for now.