A Sample of Sickness:
Richard Trenton Chase: the Vampire of Sacramento 

When David Wallin came home that night at six, he found the house dark. He entered and saw their dog, a German shepherd, waiting inside, but his wife was nowhere to be found. Oddly, the stereo was on. A bag of trash and what appeared to be oil stains on the carpet troubled him. He followed the stains to the bedroom. Then he began to scream.
His wife lay just inside the door, on her back. Her sweater was pulled up over her breasts and her pants and underwear down around her ankles. Her knees were splayed open in the position of a sexual assault. Her left nipple was carved off, her torso cut open below the sternum, and her spleen and intestines pulled out. Chase had stabbed her repeatedly in the lung, liver, diaphragm, and left breast. He also had cut out her kidneys and severed her pancreas in two. He placed the kidneys together back inside her.
There was blood in the bathroom and it was later learned that Chase had smeared Terry’s blood all over his face and hands, licking it off his fingers. The discarded yogurt container near her body was also bloodstained, as if he had used it to drink her blood. His most heinous act, however, was to stuff animal feces into her mouth. There were odd rings of blood around the body, as if someone had placed a bucket there. 

Andrei Chikatilo: 

The Heart of a Monster 

He took her to a deserted stretch of woodland and, unable to contain himself, began tearing her clothes off. As experienced as she was, Larisa panicked and tried to fend him off. Chikatilo quickly overpowered her and beat her about the head with his fists.
As she screamed, he filled her mouth with dirt and strangled her. He then bit off one of her nipples and ejaculated over her corpse. He would later tell police that he had "danced with joy" around the body until he had settled down enough to cover the body with branches and hide her clothes
After cutting out her uterus and slicing off part of her face, he wrapped the remains in her clothing and left for the party
"I felt a kind of madness and ungovernablity in perverted sexual acts. I couldn't control my actions, because from childhood I was unable to realise myself as a real man and a complete human being."
"My inconsistent behaviour should not be misconstrued as an attempt to avoid responsibility for any acts I have committed. One could argue that even after my arrest, I was not fully aware of their dangerous and serious nature. My case is peculiar to me alone. It is not fear of responsibility that makes me act this way, but my inner psychic and nervous tension. I am prepared to give testimony about the crimes, but please do not torment me with their details, for my psyche would not be able to bear it. It never entered my mind to conceal anything from the investigation. Everything which I have done makes me shudder. I only feel gratitude to the investigating bodies for having captured me." 

Hadden Clark: Cannibal, Cross Dresser, Serial Killer 

Hadden threw the little girl to the floor and was on her so fast she didn’t get a chance to scream. The first slash was a backhand, from left to right across her chest; the second went back the other way, almost like Zorro making the Z sign. She fell back in shock and he straddled her, putting his free hand over her mouth. She surprised him by biting his hand. That made him very angry and he plunged the twelve-inch knife straight through her throat. 
Blood was spurting all over the wooden floor of the little bedroom. The room in the old house sloped and the blood sought the lowest level. 
Hadden didn’t know what to do first. Should he mop up the blood and cover up what he had done or try to have sex with the dead girl? He tried the sex part first but couldn’t make it work
Adolfo de Jesus Constanzo 

His interests lay elsewhere, learning the secrets of witchcraft from his mentor. Together they robbed graves to stock the priest’s caldron and spilled blood over voodoo dolls to curse their enemies. palo mayombe is an amoral religion, drawing no line between “black” and “white” magic, leaving each practitioner to choose his own path without prejudice. Drug dealers frequently trusted its tenets to protect their outlaw enterprise, but Constanzo’s godfather had stern words of advice for his protégé. “Let the nonbelievers kill themselves with drugs,” he counseled. “We will profit from their foolishness.”