In exchange for his guilty plea to one count of statutory rape, the county agreed to drop the 18 other charges.
He faces 18 counts of murder, burglary, rape and sodomy.
The defendant had been accused on several counts of rape.
The charges were multiple counts of molestation and rape of a child.
He was charged with multiple counts of aggravated rape and held on $1 million bail.
In December 2012, he denied six counts of rape involving a girl under 16.
Simmons was indicted by a grand jury on two counts of aggravated rape.
They were all charged with multiple counts of rape because each man assisted in the other men's assaults, the police said.
She said he would be charged with four counts of rape.
In October 2010 he was found guilty of four counts of rape.