Witches have long been a fixture of medieval and pre-industrial European and American folklore and religion. According to biblical teachings and religious texts, a witch is anyone who willingly serves the devil. This means those who are found to have been possessed are not witches.
To qualify someone as a witch, a victim or witness must attest to have seen the individual willingly going against biblical or Christian teachings. This could mean that the person could have been seen performing some sort of bizarre right, reading strange texts, talking with a mysterious individual or non-Christian member of the community or refusing Christian sacraments such as communion, confession or baptism.
Usually, an inquisition or trial was held where witnesses and the accused testified before a judge. If the witch admitted his or her crime (yes, men could be accused as well, but they were far less likely) they would be spared torment or torture. Usually they were killed quickly, banished or later jailed indefinitely. If an individual was unrepentant, torture was sometimes used to extract a confession or the individual was condemned. In Medieval Europe burning was common. In the American colonies hanging was the preferred method of death.
Several signs could also qualify someone for trial. Witches usually had warts or birth marks, which were thought to be where the devil entered their body or where they nursed their familiars. Familiars were creatures that did a witch’s bidding. Usually, they were black cats, rats or sometimes bats. A person who had one of these critters around them constantly would be a great candidate for witchcraft.
Every society had its own set of signs. In the American colonies, being ugly, dancing, being a recluse, laughing or being too outspoken were all signs of witchcraft. Many historians believe that witchcraft charges were used by the male puritan establishment to crack down on feminism and to keep the community in line.
Witches in both Europe and America were believed to cause a variety of ailments, including sickening children, causing cattle or horses to die, and men to become impotent. Stories abounded of children who became sick after eating apples or other fruit given to them by older women, which led to accusations.
It was believed that Witches travelled on greased broomsticks to Witches Sabbaths where they feasted on the flesh of newborn children and engaged in grotesque sexual orgies with the Devil and with each other. A famous woodcut of the time shows a woman administering an anal kiss to the Devil.
Accusations of witchcraft had been only occasional in Europe until the religious wars occasioned by the Protestant Reformation. Shortly thereafter, Pope Innocent VIII issued a Papal Bull ordering an investigation into witchcraft because he believed that a witch had made him impotent:
It has indeed lately come to Our ears, not without afflicting Us with bitter sorrow... many persons of both sexes, unmindful of their own salvation and straying from the Catholic Faith, have abandoned themselves to devils, incubi and succubi, and by their incantations, spells, conjurations, and other accursed charms and crafts, enormities and horrid offences, have slain infants yet in the mother's womb, as also the offspring of cattle, have blasted the produce of the earth, the grapes of the vine, the fruits of the trees, nay, men and women, beasts of burthen, herd-beasts, as well as animals of other kinds, vineyards, orchards, meadows, pasture-land, corn, wheat, and all other cereals; these wretches furthermore afflict and torment men and women, beasts of burthen, herd-beasts, as well as animals of other kinds, with terrible and piteous pains and sore diseases, both internal and external; they hinder men from performing the sexual act and women from conceiving, whence husbands cannot know their wives nor wives receive their husbands; over and above this, they blasphemously renounce that Faith which is theirs by the Sacrament of Baptism, and at the instigation of the Enemy of Mankind they do not shrink from committing and perpetrating the foulest abominations and filthiest excesses to the deadly peril of their own souls, whereby they outrage the Divine Majesty and are a cause of scandal and danger to very many.
The end result of his investigation was the Malleus Malificarum, or "Hammer of Witches," written by two Dominican Friars who claimed to be able to identify witches by identifying marks.
In America, Witchcraft trials only occurred in Salem Massachusetts as a result of accusations of teenage girls who claimed to have been bewitched. The trials there were over a short period of time; in Europe they persisted for over 100 years. While only a handful of people were executed for witchcraft in America, thousands died in Europe.