But emotion is something Rader himself hadn't shown until now, reports 48 Hours Correspondent Erin Moriarty.
In Wichita, she
Moriarty spoke with Rader, 60, several times.
Prosecutors call him the "gentleman serial killer."
He's so ordinary and docile, Moriarty says, that you have to constantly remind yourself that he's also a cruel killer.
But he left no question of that during a plea hearing in June, as he calmly reeled off details of the crimes he committed.
Said Rader, at the time, of one victim: "I took her to the basement and eventually hung her. … I had some sexual fantasies, but that was after she was hung."
Hidden behind the face of the guy next door, notes Moriarty, is the heart of a cold-blooded murderer who took the lives of 10 people in Wichita.
"I manually strangled her (until she died) when she started to scream," Rader told Judge Gregory Waller about his first victims, four members of the Otero family, in 1974.
"First of all," Rader said, "Mr. Otero was strangled. … After that, I did Mrs. Otero. I had never strangled anyone before, so I really didn't know how much pressure you have to put on a person, or how long it would take."
Until he was caught earlier this year, Rader had sent letters to the police and press, calling himself "BTK," for bind, torture, and kill.
He hid from police right out in the open, working most recently as a dogcatcher.
In his office, he kept neat files on each of his victims, referred to by Rader as "projects."
Not once during the hearing did the husband and father of twoor any remorse.
But for Jeff Davis, son of Rader's last victim, Delores Davis, what matters most is an explanation.
Davis says, "The worst possible answers are better than no answers, 'cause with no answers, your mind fills the blanks."
There was no death penalty in Kansas when Rader committed his murders, so prosecutors are hoping the judge gives him the maximum prison sentence: 175 years.
Moriarty adds that Rader's family has "abandoned him."
"It's the only time I saw him show any emotion at all," she said. "He would talk about killing people and he would call them objects. He seemed to almost be enjoying all the attention.
"But he did show emotion when he talked about his family. His wife has never come to see him. His two kids have never come to see him. And he actually, when he was speaking with me, he cried when he talked about a letter he received from his daughter, saying, 'You have ruined our lives.' "