Police and the Cape Girardeau County prosecutor's office planned a 2 p.m. news conference to announce charges. Neither would disclose the suspect's name before the news conference.
Police Chief Carl Kinnison says the suspect is serving time in prison on unrelated charges and was connected to the killings by DNA evidence.
The homicides happened from 1977 to 1982, all in Cape Girardeau, about 100 miles south of St. Louis.
The bodies of Southeast Missouri State University student Sheila Cole was found in Illinois in 1977.
(Copyright 2007 by The Associated Press. All Rights Reserved.)
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