SEARCHING FOR ANSWERS: DID A HUSBAND KILL HIS WIFE -- OR IS HE THE VICTIM OF A FAMILY'S MISPLACED GRIEF? -- ON ABC NEWS' "20/20," FRIDAY, MAY 27

And: John Stossel Reports on the Gap Between Men and Women's Wages; Caught on Tape: Exploring How the Proliferation of Cameras in Our Society Has Impacted Our Lives

Why did a vibrant young mother simply drop dead? ABC News Correspondent Jim Avila reports on the mysterious death of Linda Andanalian, a 37-year-old woman with no apparent serious health problems. The original coroner could not determine a cause of death. But with what Linda's family knew about her marriage - Linda and husband Mark were having problems - and what they felt was Mark's strange behavior, it didn't take long for her family to suspect foul play at Mark's hands. Did he murder his wife of 12 years, or is he a victim of a grieving family's search for answers? The report airs on "20/20," FRIDAY, MAY 27 (10:00 - 11:00 p.m., ET) on the ABC Television Network.

Linda's sister, Meg, tells ABC News that "I could hear Linda's words saying, 'Meg, Mark has the potential of killing me and the children.'" She also says she "never saw a tear" from Mark after Linda died. Even the nanny who was hired to care for Linda and Mark's four young children noticed that Linda's pictures were nowhere to be found. A second autopsy uncovered selenium, as easily accessible mineral, toxic in high doses, in Linda's blood, liver and kidneys. The pathologist who conducted the autopsy decided that the cause of death was acute selenium toxicity; however, not all of the experts consulted agreed that the selenium found in her body was a fatal dose.

Mark declined to talk directly to "20/20." Instead he had his attorney and friend of 30 years speak on his behalf. Mark also issued the following statement: "Loosing my wife and the mother of my children has been devastating. I have fully cooperated with the Fresno Police Department regarding my wife's death. I have passed a lie detector test and have provided those results to the Fresno Police Department. I had nothing to do with my wife's death."

Meg and her family have also taken aim at the Fresno police department, accusing them of a botched investigation. Frustrated that Mark has never been arrested, charged or even been a suspect, Linda's family launched its own investigation, consulted medical and forensic experts and even hired a private investigator. The Fresno Police Department would only comment in a press release, saying: "We are doing all we can to investigate this death in an objective and professional manner."

Plus: John Stossel looks at the gap between men's and women's wages. Is sexism behind the difference, or is it something else? Martha Burke, chair of the National Council of Women's Organizations, says that companies "like to hire men... and they darn sure like to promote people like themselves." Yet Warren Farrell, a man who spent 15 years reviewing U.S. Census statistics and other studies, says that the wage gap exists not because of sexism, but because more men are willing to do certain kinds of jobs. "Women and men look at their life, and women say, 'what do I need? Do I need more money, or do I need more time?' And women are intelligent enough to say, 'I need more time...' And so women lead balanced lives; men should be learning from women," he tells "20/20."

Also: Chris Conolly explores the widespread phenomenon of people deliberately videotaping themselves having sex, including Paris Hilton, Tommy Lee and Pamela Anderson and "Survivor's" Jenna Lewis (originally aired on February 4, 2005)

"20/20" is anchored by Elizabeth Vargas and John Stossel. David Sloan is the executive producer.