Murder victim Cathy McNaughton speaks from the grave to help police ID her killer

Investigators find secret file with notes, undeveloped photos kept by Georgia woman who was stabbed to death in her home

"Everything that my mom knew about Alec was all the good things -- like everything that he had achieved, everything that he had acquired, his accomplishments," Cathy's daughter Heather Mendehall said.

At least that's what Heather thought. But in May 2006, a year-and-a-half after Cathy married Alec McNaughton, Heather had a terrifying phone call with her mother that began with a dinner invitation.

"She said that she'd love to come to dinner, but she couldn't," Heather recalled. "She sounded funny on the phone, and I just, you know, kept pushing her a little bit and she said, 'I can't.'"

Soon, Cathy confided in her daughter and told her a shocking story: that her husband, Alec McNaughton, had beaten her.

"She was on her way to work and he had violently followed her out to the car ... opened the car door and pulled her out and took her by the hair and was like literally like dragging her [by her hair]," Heather explained. "He was in a violent rage ... she said that there's no way that she could be seen in public."

But McNaughton says he and Cathy had only a small argument over a car. He says he tried to grab the car keys from Cathy in the driveway and she fell off her high heels.

"Well, she fell off her heels as we were struggling and skinned her elbow, I think, and her knee and her chin," McNaughton explained. "... she stumbled and we fell. She got scuffed up."

Heather was frightened. "I'm like, 'Well, did you call police?' She's like, 'No, I did not call the police and I'm not going to.'"

Instead, Cathy started her own investigation of Alec McNaughton and even kept a secret file with notes and undeveloped photos in disposable cameras. Police found it all hidden inside her closet.

"I took the three disposable cameras to a local developer here in the area. When I got it back, I was shocked," Fetner recalls. "There were pictures of her ... holding her hands up. And there was a huge bruise on her face and she's got bruises and scratches on her arms."

McNaughton has his own explanation for all the bruises. He says Cathy's ex-husband, Gary Mendenhall, must have done it.

But that was not Investigator Jason Fetner's opinion. Heather told him that McNaughton had beaten Cathy. Fetner knew those photos could be a key piece of evidence against McNaughton if police could answer some crucial questions, including, who took the photos?

The photographer had to authenticate the photos -- say when they were taken and if Cathy said Alec McNaughton had injured her.

Fetner wondered, "How come nobody's called to say, 'Hey, I took pictures of her when she was beaten up.'"

Police began searching for the photographer, but there were other important things in Cathy's closet: Very damaging notes about shady financial deals and worse.

"She had written down that 'he threatened to kill me,'" Prosecutor Kevin McMurry said. "She describes all the lies he's told to her."

Cathy was onto McNaughton, but she was conflicted. She compiled a list of "pros and cons" about McNaughton. And despite the abuse, under "pros" she wrote: "sweet, loving, handsome." Under "cons" she wrote: "no sex, depression, bankruptcy."

"Alec McNaughton told us that they had a perfect relationship, that they never had any physical altercations, that they were deeply in love and that they shared a wonderful marriage," said Fetner.

But that sure looked like a lie. Cathy's daughter, Michelle, says Cathy and McNaughton were having a lot of problems and argued constantly about money. "The marriage she basically was financing," she said.

And then, one night, the couple's disagreements over money exploded into a loud argument. And Alec McNaughton taped it:

Cathy McNaughton: You know, that tells you about your credit, because I never had a problem with my credit.

"I -- always carry a tape recorder in my briefcase my whole career," McNaughton explained. "She was outta control. So I just took my tape out so that, if later on, she said sumpin', I'd just play it back and say, 'You lose your temper over - minor stuff.'"

Cathy McNaughton: You started yelling first ...

"I could tell from listening to it that she did not know she was being recorded," Fetner said. "You could hear Cathy screaming at the top of her lungs at Alec."

Cathy McNaughton: ... and I'm gonna hire me a f---ing attorney.

Investigator Jason Fetner says the recording backfired on McNaughton when Cathy began referring to the time she said he beat her:

Cathy McNaughton: If you ever raise your hand to me again, to even threaten to strike me, it is over. I will get on that phone and I'll dial 911.

"She says, 'I've got pictures. I've got affidavits,'" said Fetner.

"Yeah. That was right after we'd had the struggle in the driveway over the car. So I knew what she was referring to," said McNaughton.

But as it turned out, this was not the first time McNaughton was accused of abuse, as Fetner learned after tracking down McNaughton's first wife, Linda, who had divorced Alec nearly 40 years earlier.

"And they said, 'Alec McNaughton has murdered his wife.' And my stomach sank to my toes," she said.

Despite the decades that have passed, she has never forgotten what she says her ex-husband did to her.

"He beat me with his fist, with a Coke bottle. He broke my nose. He fractured my jaw. He beat me hard," Linda told Schlesinger.

"I never abused my wife or any woman ever," said McNaughton.

The evidence against McNaughton was piling up: His past, the tape, the photos of Cathy's bruises, her notes and those cell phone records that seemingly proved McNaughton was not where he said he was on the day of the murder. Fetner called McNaughton in for a follow-up interview and the former lawyer sneered at the evidence.

"I think the comment he made was, 'There's not a snowball's chance in hell that a jury would convict me on this,'" Fetner recalled.

"Well, that's very different from, 'I didn't do this and they're lying.'" Schlesinger pointed out.

"It is. It sounds like a challenge to me."

And on Feb. 27, 2009, Alec McNaughton was arrested and charged with murder for stabbing his wife, Cathy, more than 30 times. He was thrown in jail with no bail.

"They railroaded me," McNaughton said. "They put the blinders on that night. That homicide detective, in his very first murder case ... was overwhelmed; he didn't know what to do. And he decided it was me right there at the scene, and never considered anybody else."

And now the prosecutors had one very big problem. They still had no idea who took those damning photographs. Without that crucial information, the law says the photos could never be shown to a jury. And the trial was about to start.