Gacy's mental state at the time of his crimes was questioned.

After 6-year-old William DaShawn Hamilton was found murdered in Georgia in 1999, it took 23 years to identify him and solve the case. We speak with those who never forgot about the case and pushed for justice.

We speak with experts about how conditions, like environment and temperature, affect forensic evidence when a body goes undiscovered for long periods of time.

Newlywed Lisa Techel, 23, was pregnant and asleep in bed in her Iowa home when she was shot to death by her husband, Seth, in May 2012.

The romance author murdered her husband Daniel Brophy in 2018.

Detective John Dawes speaks with us about the difference between solving active and cold cases.

Psychological autopsies, performed by forensic psychologists, are used to try to resolve cases where a murder may be mistaken for a suicide.

After Diane Staudte's husband and son died, and her daughter was hospitalized, an investigation showed she, and her favorite daughter, Rachel, were responsible for their deaths.

The reign of the bodybuilding world's most famous couple, Sally and Ray McNeil, ended after Sally murdered Ray with a shotgun in 1995.

From German nurse Niels Högel to U.K. doctor Harold Shipman to American nurse Charles Cullen, some serial killers target their patients.

Amish men are rarely prosecuted and jailed for sexual abuse against children. What's being done to expose these crimes?

We speak with Deborah Marion, mother of murdered NBA star Lorenzen Wright and Darren Goods, a lead investigator in Wright's homicide case.

The murder of a Chinese woman by her American husband in Columbia, Missouri was a long and painful case for police investigators, attorneys and, most of all, her parents.

An Airman who grew up in a Mennonite family came to resent the faith so much, he murdered a young Mennonite woman.

In October 2003, eight-year-old Josef Smith was beaten to death by his parents, Joseph and Sonya Smith. The Smiths were members of a church that promotes disciplining children in a way that some have said is abusive.

In 2010, Lawrence Ray, a 50-year-old ex-con, formed a sex cult at his daughter's dorm room at Sarah Lawrence College in New York and humiliated, tortured and trafficked members for his pleasure and monetary gain.

Detective Lindsey Wade on the experience of solving the 1986 cold case murder of 13-year-old Jennifer Bastian from Tacoma, Washington.

Robyn Maharaj, co-author of 'Grilling Dahmer' with Milwaukee detective Patrick Kennedy, tells us about the late detective's experience with the serial killer.

Author Barbie Latza Nadeau on how Italian women have played vital roles in mafia history, and have done anything—from keeping secrets to murder—for their families.

Dahmer’s murders went undetected until his arrest in 1991.