Poltergeists differ from what is normally thought of a ghost. Ghosts are usually considered to be, possibly, the spirits of dead people who can be our loved ones watching over us or the trapped and tormented spirit of a murder victim perhaps seeking just for their life being taken. An apparition of a group soldiers trapped in that final battle, or even the lost lonely little child seeking her mother…not understanding that her time has passed. Generally, these spirits pass through unaware that we even exist for perhaps we are as ghosts to them in their realm of reality.
Poltergeists on the other hand are a different sort of spirit, or entity that has little to do with the typical haunting. These particular spirits seem to be able to interact with the material world sometimes with malevolent force such as the case back in the late 1970's in England. A scientist by the name Vladistav Bukreev witnessed the harrowing and terrifying period of an English family living in London during the time period of 1977- 1978. They were plagued by severe poltergeist activity.

Dr. Bukreev saw showers of stones and bricks come down inside the house and the windows were smashed to pieces by the objects being flung through them by an unseen hand. Things would float through the air, and blood, water, and other liquid substances would pour from the walls and ceilings. The family suffered what appeared to be bite or claw marks on their bodies. The two young girls were lifted up into the air and moved around with no apparent support. For just under a year the family endured the harrowing experience but finally fled for fear of their lives leaving everything behind.
One popular notion about the nature of poltergeists is the idea that they are demons or, at least, influenced by demons. This idea was prevalent during ancient times possibly because of the striking similarities between a demonic manifestation and a poltergeist attack. Like demonic manifestations, poltergeists attacks can be sudden and obvious or gradual and subtle until their perpetrators reach their full power.
Depending on the power of a poltergeist, its activity can range from cold drafts, odd sounds, and foul smells to levitating objects, unseen hands, and physical abuse. Accounts of early poltergeist activity can be found in the work of ancient Roman writer Titus Livius, "Ab Urbe Condita," wherein a shower of stones scared the Roman army. Other notable records of poltergeist activity involving people being dragged away from their beds by unseen forces and of unexplainable fires were written by Jacob Grimm in his work "Deustche Mythologie." Given the largely superstitious atmosphere of that time, poltergeist activity was readily attributed to demonic powers.
But the progress of paranormal science and parapsychology during the 20th century gave rise to a new concept about the nature of poltergeists. Separate studies done by parapsychologists Nandor Fodor, Alan Gauld and A. D. Cornell, and William Roll traced poltergeist existence and activity not in paranormal entities but in humans. According to their theories on the human-poltergeist connection, the force usually ascribed to poltergeists are powerful emotional and mental triggers in the human psyche. These theories have their foundations on the idea that poltergeist activity usually occurs in places which have seen much violence and suffering or around persons who are experiencing deep emotional turmoils.
Roll even went as far as to name the phenomenon as "recurrent spontaneous psychokinesis" or RSPK. This refers to the expression of intense emotion like hostility, anger, and sexual tension from a human agent which causes inexplicable physical manifestations such as levitation. The agent is usually oblivious to the fact the he or she caused the disturbance because it is the subconscious mind which found a way to release any repressed emotion through psychokinesis.

On the other hand, poltergeist activity without the presence of an agent is attributed to the remnants of intense emotions in a particular locale, a phenomenon similar to how a place gives one "the creeps" without any apparent reason. In this case, poltergeist activity is simply an outward manifestation of human emotion. It is perfectly controllable as long as the agent expresses pent-up feelings, hence, lessening chances of subconscious "poltergeist" activity.
Many believe that a poltergeist is an elemental type creature, something very much akin to what would be called the Fae in Irish folklore. Still there are others who say a poltergeist is something generated by a young girl or boy just hitting the turbulent teen years when the physical and emotional changes are very stressful and the teenager in question is unconsciously releasing psychical energy in such a way as to actually affect their surroundings.
Despite the differing opinions about the nature of poltergeists, one thing is definite -- they do exist. Whether poltergeists are paranormal entities or psychic forces, they continue to be one of the most popular and interesting paranormal "beings" in ancient and recent history. What are they? Nobody knows exactly but this mystery is one good reason for people to be on their guards.

Demonic Possession
It is widely believed that demons, unlike ghosts, are able to inhabit and take control of humans at any time. Furthermore, it is believed that people have no control over this matter or what may happen once a demon or demons have taken control.

Cases of demonic possession have been reported for centuries. Demons and demonic possession can be traced all the way back to the ancient sumerians who would pray to gods for the protection or release of certain demons. They also believed that all illness, both mental and physical was caused by demons called sickness demons. Evidence of this can be found in ancient writing on tablets.

In the modern age, the catholic church performs exorcisms on an almost daily basis. What used to be only a small number of priests authorized to perform exorcisms has grown to well over 350 in recent years. All exorcisms require approval of a bishop. The church has been one of the biggest skeptics of such events over the years and the rise in numbers is surprising. What does this mean for humanity? Is there a growing number of demonic possessions within our modern world? Many reverends and pastors from other christian religions are known to regularly participate in the "casting out" of demons as well. Demonic possession is not only limited to the christian religions. Demonic possession is a belief and various forms of exorcisms are done in many cultures around the globe.

Pre existing mental conditions have been blamed by most skeptics for suspected demonic possession. There is even a mental disorder called "demonamania" in which the victim believes that he or she has been possessed by one or more demons. So are all people who have been possessed simply "mental"? What about all of the witness to such events?

Strange and scary things have been reported during cases of demonic possession, such as the victim speaking in a foreign tongue, or in a voice that does not resemble their own. Many victims of demonic possession suffer wounds which are often self inflicted, but many have been witnessed manifesting without human interaction. Furniture inside of the victims house has been said to move or turn over. This includes items as big as refrigerators. How does a mental condition explain all this? Skeptics think that witnesses could be suffering from mass hysteria. What do you think?

In 1897 a ghost's testimony convicted a man to life in prison

Elva Zona Heaster was found dead on January 23, 1897. When the doctor and coroner arrived an hour later, her husband, Edward Shue, had moved her body to the bedroom and dressed her for burial. He dressed her in a high-necked dress with a stiff collar, placed a veil over her face, and covered her neck with her scarf. When the doctor and coroner arrived, Shue was sobbing so hard that the body was only given a brief examination. The only thing determined was that there was bruising on the neck. Shue wouldn’t let the doctor look any closer. Elva's parents were told about her death, and this is where the story gets stranger.
Four weeks after the funeral, Elva appeared to her mother in a dream. She said that Shue was a cruel man who abused her and had broken her neck when she didn't cook meat for dinner. The mother convinced the prosecutor to exhume Elva's body and perform an autopsy. The autopsy confirmed that her neck had been broken and her windpipe smashed.
Shue was brought to trial for murder on June 22, 1897, and Elva's mother was the star witness. Shue's lawyer tried to prove Mrs. Heaster unreliable, but she wouldn't waver in her recounting of the ghost story. The judge tried to get the jury to discount the ghost testimony, but it was difficult to poke any holes in it, because Elva's mother was so consistent in it. Because the autopsy had revealed that she had actually died of a broken neck, the story was considered very credible, and Shue was convicted to life in prison.