Why did I not include these additional three people on the list? The reason is that these three people did not lay in state. They received a similar but different recognition which is know as laying in honor.
(Rosa Parks laying in honor in 2005.)
Wikipedia has the story. It notes, "The United States Congress has recently created a similar -- though not identical -- privilege for distinguished Americans who don't quite qualify for a "lying in state" designation. Congress may permit an individual to lie in honor in the Rotunda and has done so for three individuals to date. In 1998, a mentally unstable man named Russell Eugene Weston Jr. stormed the U.S. Capitol building and shot and killed two members of the United States Capitol Police, Officer Jacob Chestnut and Detective John Gibson. In response, the U.S. Congress provided for their remains to lie in honor at the Rotunda. In 2005, upon the death of civil rights activist Rosa Parks, Congress permitted her remains to lie in honor at the Rotunda, too."
Indeed, Rosa Park, Jacob Chestnut, and John Gibson did lay in honor at the US Capitol. But they did not lay in state as they did not qualify for that honor. At least I hope this settles this debate in my department anyway.