Lorenzo J. Gilyard, 53, was charged Saturday with 10 counts of first-degree murder and two counts of capital murder, the law in effect at the time of two of the killings. If Gilyard is convicted of all the murders, he would be the worst serial killer in the city's history, police said.
He was being held without bail.
DNA comparisons prompted investigators to link Gilyard to the killings April 12, according to a probable cause statement filed in Jackson County Circuit Court. He was arrested Friday, authorities said.
The victims' ages ranged from 15 to 36. Eleven were prostitutes, according to court records. The 12th victim was mentally ill and often walked the streets and accepted rides from strangers.
Nine of the victims were found nude or nearly nude; some were bound or had something tied around their necks; some were found wearing only shoes and socks. Eleven of the dead were sexually assaulted and some of the bodies were posed.
Officials said Gilyard was married, lived in south Kansas City and worked as a supervisor for a trash-collection company in Kansas.
A blood sample was taken from Gilyard in 1987, but the technology to link him to the killings did not exist until 2000, officials said. Police would not say why the sample was taken from Gilyard in 1987, when he was one of several men from whom blood samples were collected.