Advancement in science and technology are encouraging people to revisit the past in hopes of answering questions that have remained unanswered. Techniques from the 20th century are applied to cases dating back as far as ancient times.

Killers often will try to cover up their crime by hiding the remains of their victims. Sometimes bodies may lay hidden for years before they are discovered. That’s when forensic scientists are called upon to reveal buried clues.

At the scene of a murder, sometimes the only clues to the killer come from the victim. Forensic anthropologists use skeletal remains to decipher the clues written in the bones to bring the murderers to justice.

Sometimes, the wrong people are punished for crimes they did not commit. Forensic scientists use DNA analysis to overturn convictions of these innocent men and women who have spent years behind bars.

A tool used to commit a crime can often be the same tool used to solve it. The pattern a machine leaves on an item, the unusual way a tool crimps a wire and even something as innocuous as the shape of a wood chip can lead to a killer.

Marriage is one of the tightest bonds two people can have, until lies and deceit drive one of them to kill. In this episode, forensic experts are employed to link a woman’s husband to her violent murder and uncover a murder disguised as an accident.

The most sacred of vows are sometimes not enough to stop a serious desire. In this episode, a nurse suspects a patient’s husband of attempted murder by poisoning and a man stages his depressed wife’s murder as a suicide.

The law enforcement agency of the United States Navy and Marine Corps uses forensic science to solve perplexing murders and fulfill their motto: “To the living we owe respect; to the dead, we owe the truth.”

A dog can be a dead man’s best friend. Some dogs have been trained by law enforcement to sniff out corpses, drugs, explosives and missing persons. Even with advances in science, a dog’s nose is often first to find fundamental clues.

Young men shipped off to war would never return. Forensic experts work to tell their stories.

It is difficult to convict a murderer if the body can’t be found, but forensic science is finding ways to do it. A speck of blood, a piece of a fingernail or a strand of hair may now be enough evidence to prove a murder and capture a killer.

Most victims are meticulously chosen by their murderer because of a connection or because they match a set of criteria. The most terrifying cases of murder occur when the killer appears to choose victims at random.

Murderers will go to great lengths to keep their crimes concealed, but forensic evidence is impossible to cover up. In this episode, authorities rush to identify bodies found in drum barrels and locate several missing women linked to the killer.

Approximately 1.8 million Americans are reported missing each year. Some are runaways who eventually find their way home but others simply disappear without a trace. When foul play is suspected, investigators turn to forensics to find the missing.

Philadelphia’s Vidocq Society, named after an 18th century French detective, is one of the world’s most unusual crime-solving organizations – a members-only club made up of forensic professionals. Witness these sleuths solve impossible cases.

Often killers are careful to not leave any fingerprints behind. But the methods of the murder itself can leave a lasting impression on authorities, especially when the tools of a killer’s trade leave a victim marked for death.

A killer will often try to disguise the victim’s body in an attempt to the hide the actual cause of death; however, forensics cannot be fooled. In this episode, authorities use reverse DNA testing to identify remains and solve an old crime.

Blood can be the most telling evidence of a murder and often it is the only thing investigators have to link a killer to his or her victim. Forensic scientists and medical examiners look at blood spatter patterns to determine how someone was killed.

With DNA analysis just a few microscopic cells found at a crime scene can be used to convict a killer. Forensic scientists can analyze droplets of blood, hair fiber, or a piece of chewed gum to determine the identity of a victim or killer -- or to prove innocence.

Missing Person: In America nearly 1.8 million people are reported missing each year, factor in the world and that number triples. Using computer databases and other means victims are found, laid to rest…or never seen again.

Ballistics: A body with a gunshot wound to the head, the gun is next to the body. Was it suicide or murder? Every part of the gun can be analyzed for the correct answer.

For some killers, once is never enough. Often, cold and calculated serial killings are more difficult to solve than violent crimes of passion. For investigators, the challenge is steep when the killers murder by numbers.

Lies, deception and contradicting witnesses can often throw investigators off the trail of justice. But when indisputable evidence refutes a killer’s story, police must use the clues to piece together the truth.

Explosives Investigations: A woman opens a box which explodes killing her. Soon to follow are five other bombs just as deadly as the first. This soon turns into a massive investigation leaving the experts to sift though the evidence.

Plants help provide oxygen and nutrients for existence. In criminal investigations, a simple seedpod can provide the missing link by placing a suspect at a crime scene. Dirt left on shoes, tires or clothes can pinpoint a crime scene.