Deneb V or Deneb Kaitos V is a Class M planet located in the Deneb Kaitos system. The planet is home to a humanoid species known as the Denebians. It's official name is the Commonwealth of Denebia. (Star Trek: Star Charts)
In the 2260s, the Denebians still practised the death penalty for a multitude of crimes, including fraud. The condemned would either by electrocuted, gassed, or hung. In 2267, Harry Mudd was sentenced to death of Deneb, but managed to escape before his sentence could be carried out. (TOS episode: "I, Mudd").