Dr. Michael Amar, once a respected surgeon, went crazy and started a killing spree to stop the voices in his head. This spree went through Central City and Keystone City and caught the eye of police officers Fred Chyre and Joe Jackam. They later tracked Amar down with help from the Flash and Amar was convicted and sentenced to death.
It was soon discovered that Amar's blood was so abnormal that lethal injection could not kill him. Later, in Iron Heights, Amar cut out his own tongue and sewed his mouth shut, becoming the killer known as Murmur.
While in prison, Murmur created a virus that was killing the guards and prisoners and escaped during the riots it had caused. He then joined Blacksmith, who helped him with creating the virus, and her rogues. Afterwards, Murmur struck out on his own.