Turns out that one of the 18, Sen. Mary Hodge of Brighton, was actually opposed to the death penalty, but she voted no anyway, according to this Denver Post story by Jessica Fender.
Hodge said she's anti-death penalty but didn't agree with using its demise as a way to help solve cold cases.
"It's the hardest vote I've ever taken," Hodge said. "I felt that the two issues are not connected. I think it's taking two sets of victims and pitting them against each other."