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.

Some people murder for love, others murder out of hatred. But sometimes people kill for the money. When greed is the motive, investigators must make every clue pay off in these murder-for-profit cases.

When there’s a difficult case to crack, agents of the Bureau of Alcohol, Tobacco and Firearms can be called in to help. These investigators have the means to tackle crimes involving drugs, arson and weaponry.

Poison is the subtlest murder weapon and poisoners are sometimes the most brutal killers, harming their victims over time to disguise the murder. Investigators must see through the unusual circumstances to bring these murders to light.

When lovers turn on each other or marriages fail, some coldblooded spouses find a gruesome way to gain an uncontested divorce: murder. Forensic scientists must piece together the mystery of love gone awry to catch these killers.

The great outdoors may offer clues to solving heinous crimes. Seed germination and the presence of certain insects provide vital information about murders. It takes the skilled eyes of a forensic entomologist and botanist to decipher nature’s clues.

There’s never a good reason for murder but some killers are especially cruel – choosing their victims at random or with no apparent motive and then expertly covering their tracks. These crimes may seem unsolvable, but telling clues remain.

There’s no statute of limitations on murder, so as a case turns cold and clues become scarce, investigators must rely on modern forensic technology to solve the crimes and catch the killers.

Every family has its secrets and sometimes blood relations lead to bloodshed. When murder becomes a family affair, investigators must turn to science to uncover family plots.

Sometimes arson fires are set to cover a different, more heinous crime – such as murder. But killers are wrong to think that fire destroys all vital clues. Arson investigators can pull evidence from scorched rubble to ignite the flames of justice.

Solutions to atrocious crimes can hinge on the smallest of clues. Even with advanced technology, vision remains an important tool. Forensic investigators must train their eyes to find the full story of a murder written in a single scrap of evidence.

What does it take to prove murder if the victim cannot be found? Forensic investigators must go to great lengths to catch the killer when the victim is only presumed dead.

There’s an old saying that a burden shared is a burden halved. But when people team up to commit murder, the weight of their guilt remains just as heavy. Investigators must rely on forensic science to capture partners in crime.