Some are cozy, some are cluttered, some are meticulously clean while still others can be a bit messy.

Most homes are filled with reminders of the lives lived there; photographs, knick-knacks, favorite T-shirts stuffed into drawers.

How can someone turn into such a monster What drives an otherwise normal human being to become a killer For all the science dedicated to understanding what makes these monsters tick, one important aspect of their life is oft-forgotten: their home.

But for other career killers, we often forget about the places in which they spent so much time of their twisted lives.

Still, after their crimes are uncovered neighbors will often come out of the woodwork, as it were, to say they always got a bad feeling about their murdering neighbor.

Suddenly your neighbor with his constant partying doesnt sound bad at all eh.

But these kinds of crimes arent limited to within the borders of the United States.

From 1978-1983, Nilsen claimed the lives of at least 12 men, and attempted unsuccessfully to kill at least seven others.

He would lure them to his house, sometimes suggesting they get drunk with him, and then strangle them.

If the victim was still alive but unconscious after being strangled, hed drown the poor guy in a bathtub and proceed to get freaky with the body.

He actually is partially to blame for his own arrest, as he complained to his landlord about plumbing problems.

When a plumber investigated why the pipes were in such bad shape, he discovered a blockage of flesh and small bones.

When this blockage was brought to Nilsens attention, he told the plumber It looks to me like someone has been flushing down their Kentucky Fried Chicken.

Its looked haunted and unlivable for about 20 years, said Sharon Sullivan, a former neighbor.

Neighbors thought the home was an eyesore, and did not hold the homes owner in high regard.

I never thought when I talked to him that I was talking to a normal human being, said one neighbor.

He murdered his first victim in 1978, a 9-year-old girl named Yelena Zakotnova.

After making contact with her, the future cannibal killer promised her bubblegum if he followed her to his shack, which was nearby.

When they arrived, he attempted to have sex with her, failed, stabbed her to death, and then threw her body into a nearby river.

Her body was discovered two days later and investigators even found spots of blood outside of the shack in the course of their investigation, however Chikatilo was obviously never charged with the crime.

He would go on to lure even more victims into this same spot.

He was born in what was then Germany in 1870, though that area is now part of modern-day Poland.

He was arrested in late 1924 after attacking a man with an axe at his home, it was at this point police discovered jars of human flesh curing in jars within the home, as well as various pieces of meat and bone.

Andrei Chikatilo Murder Photos