For six years, a serial killer prowled the streets of New York City, hunting his victims. He promised to kill 12 people, one for each astrological sign. And he only struck while certain constellations were visible. It took forensic astronomy, handwriting analysis, and a World War II code breaker to find him.

The episode was rated 7.69 from 16 votes.

The Boczkowski Case. A woman’s death in Pennsylvania triggers a homicide investigation into another woman’s death in North Carolina. The similarities in the cases were striking, and medical examiners must determine if the suspect’s story about accidental drowning is all wet.

The episode was rated 7.71 from 21 votes.

For years, a woman suffered from what appeared to be the unpleasant side effects of lithium, a drug prescribed to treat bipolar disorder. Her search for help led her to numerous doctors and hospitals, and resulted in a 4,000-page medical file. When she died, investigators had to determine if her death was due to natural causes, suicide, or murder.

The episode was rated 7.75 from 28 votes.

A 34-year-old nurse experiences a variety of flu-like symptoms. None of her doctors are able to discover the cause, until she visits the gynecologist for a routine check-up. She then learns it's something far worse than the flu. She is HIV-positive. Being a nurse, she could have contracted the HIV virus in any number of ways. In the end, science was able to determine not only how she had been infected, but also by whom. The worst part: it wasn't an accident.

The episode was rated 7.76 from 33 votes.

When a teenaged girl is found dead on the side of the road, her boyfriend becomes the prime suspect. He eventually confessed to her murder – but so did another man. It would take the passage of forty years, an author, and an expert in the field of pedestrian accident reconstruction to determine who was telling the truth. Originally aired as Season 8, Episode 36.

The episode was rated 7.85 from 20 votes.

The double homicide of a gay couple leads investigators into the twisted world of White Supremacists. Shell casings, paint chips and an analysis of glass shards help authorities link their prime suspects to a string of hate crimes in California. Originally aired as Season 8, Episode 17.

The episode was rated 7.86 from 21 votes.

When firefighters found an entire family dead inside their home, it looked like a murder/suicide. But there were several inconsistent clues inside the rubble. Could ballistics, a time card, and some secret audio tapes unravel the mystery?

The episode was rated 7.88 from 24 votes.

A retired police officer is discovered in his bed, dead of a single gunshot wound to the head. His wife first says the motive was robbery; then she tells police he committed suicide. It would take careful examination of the evidence at the crime scene, the tape from a bank surveillance camera, and forensic textbooks found in the victim's home to write the final chapter of this real-life whodunit.

The episode was rated 7.89 from 18 votes.

The murder of a prominent business man in Colorado was particually difficult to solve since the killers left virtually no forensic evidence at the scene. But information gathered from a small-town diner, an endocrinologist, and a forensic botanist took a bite out of the chief suspect's alibi.

The episode was rated 7.93 from 28 votes.

When a small child disappeared in Alaska, investigators were initially unsure whether the cause of a grizzly bear or an abduction. The discovery of a fiber, a piece of molten steel, and a chip of yellow glossy paint pointed police in the direction of a human. But others weren't so sure.

The episode was rated 7.95 from 20 votes.

In 1986, Jeanette Kirby was brutally murdered while jogging in a Michigan park. Her assailant used unusual police-style handcuffs to subdue her before stabbing her to death. It took over 15 years for police to bring her killer to justice, using forensic science.

The episode was rated 7.96 from 27 votes.

Ray Krone was known throughout Arizona as the snaggletooth killer. An unusal bite-mark on a murdered woman resulted in his conviction and death sentence. A forensic expert told the jury that he was 100% certain that it was Krone who bit the victom. But the expert knew he was wrong and confided to a friend ""I'm too commited, and now I'm in too deep.""

The episode was rated 7.97 from 30 votes.

Niantic, CT: A woman is found dead in her home while her husband is out on a sailing trip. When investigating, police uncover a lifestyle of sex parties and wife swapping. Forensic investigators begin to solve this crime with a old movie, an overheard phone call, and an air conditioner.

The episode was rated 8.00 from 19 votes.

With no forensic evidence found at a murder scene, investigators were baffled. But they suspected that the victom's dog had witnessed the crime. If she had, forensic scientists needed some way to find out what the dog had seen.

The episode was rated 8.04 from 23 votes.

A drive-by shooting leaves one man dead and another seriously wounded. Cell phone calls and shell casings point to a suspect, but authorities are unable to place him at the crime scene. When a forensic geologist compared soil from the crime scene with soil found in the wheel wells of the suspect’s car, he proved that dirt is anything but dumb. Originally aired as Season 8, Episode 35.

The episode was rated 8.33 from 24 votes.