When court clerk Peter Porco doesn't report to his work in November 2004, a courts officer is ordered to the Porcos' family home in Bethlehem, NY. Inside the home, he finds murdered Peter Porco and his barely alive wife Joan who had both been savagely attacked with a fireman's axe. Eventually, a DNA sample may lead to the killer.

When a college student is reported missing, police believe their investigation will be like countless others, and she'd turn-up a few days later. But when they discover blood spatter in her boyfriend's bedroom, blood spatter someone had gone to great lengths to conceal, they know this case is going to be different.

In 2006, Nevada politician Kathy Augustine died mysteriously during a hard-fought re-election campaign and the medical examiner could neither isolate the cause of death, nor explain the tiny puncture wounds discovered during the autopsy. Upon deeper analysis, investigators focus on her husband Chaz Higgs, a critical care nurse who had ready access to succinylcholine.

In 1999, Patrick McRae was found dead in his Des Moines home and the crime scene was awash with blood. Analysis showed it had come from two people, one of whom was female. The male DNA was McRae's, which meant the killer was a woman. Leads dried up and the case went cold until a suspect arrested for drug possession offered police a deal, and told a bizarre tale of an exotic dancer named Andrea Morris who listened to the voices in her head.

In 2000, the body of exotic dancer Rachel Siani was found beneath a New Jersey bridge and investigators wondered if she had committed suicide. Evidence at the scene proved not only that she'd been carried to the bridge and thrown over the side, but also that she was alive when she fell. Police look at customers at the gentlemen's club and co-workers who had vendettas against the victim.

A young woman is found dead in her apartment. There's little evidence at the scene, leads don't pan out and the case turns cold... until police discover a link between their prime suspect and an unsolved murder committed six years earlier in different state.

Detectives think they've solved a murder when they find the weapon and victim's blood in a man's flat, but the evidence may have been planted.

Doctors don't know why a young scientist is gravely ill. When tests finally reveal the cause, it's too late to save him. Police hope that lab analysis of his hair, showing when attempts were made on his life and what was used, will lead to the killer.

In 2004, Mary Ann Clibbery was found brutally murdered in her Illinois business and investigators had to determine if this was a robbery gone wrong or a calculated murder. The evidence at the scene told police what happened and they got a huge break when evidence from the murder was found on top of a nearby frozen river.

In 2006, Texas real estate agent Sarah Anne Walker was found brutally murdered in a model home. Weeks later, a witness came forward who may have seen the killer and police used forensic hypnosis to help him recall every detail of the man's appearance. His description was used to create a composite sketch, which police used to draw the killer out of hiding.

In 2003, St. Cloud teenager Jason MacLennan returned home after a night out with friends and discovered his father Ken's body lying in a pool of blood. There were shoe impressions outside in the new-fallen snow; because the victim's wallet and watch were missing, the motive may have been robbery. But before making that determination, police needed to find out who had the most to gain from his death.

In 1996, Virginia Beach police arrive at the Makdessi apartment to find Elise Makdessi and her lover Quincy Brown dead. Elise's husband Eddie had reported that he killed Quincy Brown in self defense after Brown had murdered Elise. Eddie gave the police a videotape Elise had made a week before, alleging that she had been the victim of sexual harassment and assault while in the Navy. Investigators found evidence that her allegations may have been part of an elaborate scheme for financial gain. Hoping to separate fact from fiction, they turned to forensic science.

In 2000, construction manager Darrell North was found dead in his work trailer in Ft. Worth, Texas. When investigators arrived, they found that he had been stabbed 46 times, described as overkill and indicating a personal relationship between the victim and the attacker. Police hoped that, during the struggle, the killer had left some of his own blood and his DNA behind. Their challenge was to find it. Forensic science points to an unlikely suspect.

In 2000, Judy Southern arrived home from work and was shot by a gunman waiting within. Her husband Allen arrived shortly afterwards, called 911 to report his wife had been shot and drove her to the hospital. She died on arrival and the investigation focused on her husband Allen, but forensic analysis and a suicide note found at the scene pointed to the killer.

In 1986, Gary Dale Larson was stabbed to death in his Edmond, OK, home and then the killer sexually assaulted Larson's girlfriend Janet Haynes. Hayne's story seemed farfetched: The perpetrator was wearing only underwear and gloves broke into the house, stabbed Larson to death, then raped and terrorized her for hours afterwards. But, the evidence at the scene supported her story, and investigators turned for help to the FBI and their criminal profilers.

In 1991, Dorothy Donovan was murdered in her Dover, DE home and police are skeptical when her son Charles Holden stated that she was murdered by a hitchhiker he had picked up. Their suspicions were heightened when he refused to take a polygraph test and they turned to forensic science. Would the blood and fingerprint evidence at the crime scene support Charles' story or prove his guilt?

In 2001, Ginger Hayes and her infant son Nicholas were abducted during a carjacking and the crime had been reported by a witness within minutes of occurrence. 45 minutes after the kidnapping, When Ginger and Nicholas were found 50 miles away, Ginger had been beaten to death, but Nicholas was still alive. Further analysis of Ginger's car and evidence at the scene where Ginger was found both led to her killer.

In the early hours of a morning just before Christmas, a college co-ed was abducted from the parking lot of her apartment. Her body was found later that day; she'd been sexually assaulted and then shot at point blank range. Eight long years passed and then a pair of running shoes and a cell phone breathed new life into a very cold case.

A serial rapist is on the loose in a Texas town. No one knew where he'd strike next, but the audacity of his attacks and the escalation of violence against his victims made finding him imperative.

The victim has been stabbed more than thirty times, and the crime scene is awash with her blood. Near her head, police discover a distinctive button with strands of thread still attached. If they can find the owner of the shirt the button came from, they'll also find the killer.

A young woman attends evening church services... then disappears. When her abandoned car is found, the tank is empty and a gas can she kept in her trunk for emergencies is missing. Eyewitnesses place her at a nearby gas station, getting into a van, but their descriptions of the vehicle don't match. Three days later when her body is discovered, the search for the driver of that van intensifies.

When a nine-year-old girl goes missing, police and volunteers spend weeks searching for her. A psychic's vision leads to a field where her body is discovered, along with what investigators hope is enough evidence to help them to also find her killer.

Digital enhancement of security camera video shows that what appears to be a casual encounter is actually a forced abduction, leading to murder. The perpetrator's M.O. is remarkably similar to another murder which occurred five months earlier, 15 miles away. When investigators learn the crimes might not be isolated or random, they also realize a serial killer may be on the loose.

The woman had been sexually assaulted, stabbed repeatedly, and left for dead. She survived, and gave police a detailed description of her attacker. When someone who fit that description practically turned himself in, police were sure they had their man... until the DNA evidence proved them wrong.

The victim was a self-made man who never minced words. Perhaps he was murdered by a disgruntled client or employee. Perhaps the racy photos in his safe held the clue to solving the crime. Or perhaps with the help of the IRS, investigators could follow the money and find the killer.