Produced by Lourdes Aguiar and Sara Ely Hulse
[This story was first broadcast on Sept. 29, 2012. It was updated on May, 4, 2013]
"48 Hours" has pursued this case for five years ... turning up the heat on a cold case and a murder suspect.
It's taken 10 years to get Hailey Sisco's mother, Dana Chandler, into a Topeka courtroom to face trial for murdering Hailey's father, Mike Sisco, and his fiancee, Karen Harkness.
"She's being held accountable for what she's done - and I - I hate that that's the truth, but it is," an emotional Hailey Sisco told "48 Hours." "Your mom did kill your dad. That's - that's the fact."
Hailey was just 17 and her brother, Dustin, was 15 at the time of the murders.
"I know mom did it," Dustin told "48 Hours" correspondent Richard Schlesinger.
"And you've known that for 10 years?" Schlesinger asked.
"Lord knows I don't want it to be her," Hailey said. "If it wasn't I would be on cloud nine."
The question is, will prosecutors be able to convince the jury that Dana Chandler is a murderess?
"Convict her. Because she killed Mike Sisco, she killed Karen Harkness and she robbed her own children of their father and his fiancee," prosecutor Jacqie Sprading told the court.
But here's the problem with the case. There's absolutely no physical evidence - no DNA, no fingerprints and no witnesses; Almost no way at all to place Dana Chandler at the crime scene.
"48 Hours" first reported on this story in 2009, with our late colleague Harold Dow. It was a cold case then:
Harold Dow: "Did you know anything about the death of Michael and Karen?"
Dana Chandler: "I have no idea what happened to Mike and Karen."
Harold Dow: "There are some people out here that think you had something to do with it."
Dana Chandler: "I know that."
"48 Hours" was first to publicly name Dana Chandler as the prime suspect.
She sure seemed like the perfect suspect. Dana and Mike were married for 16 years, but went through a long and especially ugly divorce. She lost custody of Hailey and Dustin when the court ruled that Mike was the more stable parent.
"My dad was really my life growing up," Dustin explained. "He was really my hero."
Mike, 47, sold welding equipment.
"He had a wonderful sense of humor. He kept his humor no matter how he felt inside," Carol Sisco said of her son. "I see the pain in my grandchildren's hearts with him gone. And we just - we just miss him so much."
Mike had been dating Karen Harkness for four years. She was 53, also divorced, and the mother of two grown children.
"They were extremely happy, you could just see that. You know, everything they did was for each other," said Harold Worswick, Karen's father.
On July 7, 2002, Worswick and his wife, along with Carol Sisco, were meeting the couple at Karen's house expecting an announcement - that she and Mike were finally engaged.
"And I rang the doorbell and knocked on the glass and couldn't raise anybody. I thought, 'this is strange,'" said Worswick.
They went around back and found the sliding glass door open. Inside, there was no sign of either Mike or Karen - at first. Then Harold Worswick went downstairs to the couple's bedroom.
"Just as I got to the foot of the stairs, I could see Karen," Worswick said. "And I said, 'Oh, Christ.' I knew she was dead ... And then I found Mike on the outside of the bed."
Mike and Karen had been shot 11 times.
"The number of shots was the particular important thing there I felt, that it was overkill," lead detective Richard Volle explained. "It told me that there was some emotion involved in it."
Police were able to quickly rule out robbery as a motive, because they found cash along with Mike's Rolex and Karen's jewelry untouched.
"There was no profit motive in this. This was pure revenge," said Det. Volle.
Investigators started looking for someone with a grudge against one or both of the victims.
"We began looking at the victim's families," Det. Volle explained. "They were interviewed and ... they cooperated fully in the investigation."
Asked who did that leave him with, Det. Volle told Schlesinger, "That left us with Dana Chandler."
Mike's sister, Cathy, and her husband, Mark Boots, have a lot of experience with Chandler. They say Dana stalked Mike.
"She is truly evil," said Cathy Boots.
"I think she became obsessed with the fact that Mike was moving on with his life. And she was not seeing the fulfillment in her own life for whatever reason," said Mark Boots.
Sometimes the stalking was just annoying and sometimes it was more. Cathy still remembers one night years ago when she was staying with Mike during the divorce.
"The kids were upstairs in their rooms," she recalled. "And - we heard a noise and there she was in the middle of the night ... Jumping on a trampoline in the backyard of Mike's home."
"Was she saying anything while she was jumping on the trampoline?" Schlesinger asked.
"Just laughing," Cathy replied.
"Yeah, just laughing."
"And then when Karen entered the picture, that's when things really started, I think, escalating," said Mark.
Dana's surprise appearances became so frequent that Mike started keeping track in a journal:
July 28, 1998: Dana stalking neighborhood at 8:30, caught her she left.
Nov. 12, 1998: Dana came in house while I was at Karen's from 7 to 11, went through stuff, caught her walking out back door when I came in, called police.
"All this harassment and -- stalking had come to the point that Mike told me that he and Karen now feared for their lives," said Mark.
The last time she showed up was one month before the murders. Mike found Dana inside his house drinking a cup of coffee.
"She said, 'The kids are getting older. ...They're havin' different issues with themselves now. They need both parents. I think I should move back in and we should parent together," Cathy told Schlesinger.
"And he said?"
"'Are you f---ing crazy? I'm marrying Karen,'" she said.
"Was that the first time he told her that he was marrying Karen?"
"I think it was," replied Cathy.
"We think it might have been," added Mark.
Mike's family believes that final rejection pushed Dana over the edge. But at the time she was living eight hours away in Denver and Topeka police still had no evidence linking her to the murders. Then Detective Volle talked to Dana. It wasn't what she told him ... it's what she didn't tell him.
"She didn't tell me about the gas cans, because she didn't want me to know about the gas cans," he said. "So my assumption is, that there's something about the gas cans that is important."