The death penalty doesn't deter crime. Many innocent people are exonerated from death row due to "mistakes" made in their cases, or by corrupt investigators. I do not want to be responsible personally for an innocent person being put to death, and I do not want my tax dollars spent on a new gas chamber in Las Vegas.
More background is here:
http://lasvegassun.com/news/2015/may/18/lawmakers-split-funding-new-execution-chamber-ely/