Among the more common questions we’re asked is, “What is spectral evidence and what role did it play in the Salem witch trials?” First let’s get a working definition. US Legal.com : http://definitions.uslegal.com/s/spectral-evidence/

“Spectral evidence refers to a witness testimony that the accused person’s spirit or spectral shape appeared to him/her witness in a dream at the time the accused person’s physical body was at another location. It was accepted in the courts during the Salem Witch Trials. The evidence was accepted on the basis that the devil and his minions were powerful enough to send their spirits, or specters, to pure, religious people in order to lead them astray. In spectral evidence, the admission of victims’ conjectures is governed only by the limits of their fears and imaginations, whether or not objectively proven facts are forthcoming to justify them. [State v. Dustin, 122 N.H. 544, 551 (N.H. 1982)].”

We know that the Court of Oyer and Terminer, formed in June 1692 for the purpose of hearing cases awaiting in Boston’s jails backlogged while the Charter with England was being hammered out, recognized spectral evidence despite that it was not in keeping with generally accepted procedure of the time. In Law and People in Colonial America Peter Charles Hoffer offers this characterization (p. 41):

“The result of having laymen on the high-court benches might be…swift and sensible justice. Massachusetts superior Court justices, such as Samuel Sewall, were deeply moral men, concerned about the quality of their performance. Sewall was typical of the best lay judges – well traveled, well schooled, much respected, and experienced in colonial government and in hearing and deciding lawsuits, if not learned in the law. In the Salem witchcraft tirals of 1692 the judges, including Sewall, departed from current, learned, English practice, and did so with tragic consequences. There were no trained lawyers on the bench, but all believed that there was a devil and that he contracted secretly with men and women to do his evil work in the colony. Thus, at least in theory, witches had the power to leave their bodies and in spectral form assault their victims.”

The following passage from another of Hoffer’s works the Salem Witchcraft Trials: A Legal History is further clarifying (page 78-79):

“Mather elected to straddle the [spectral evidence] controversy rather than resolve it. …Mather fretted, “Our neighbors at Salem are blown up after a sort, with an infernal gunpowder, under the floor.” What could that mean? To us the reference may be obscure, but to his fellow Puritans the implication was obvious. In 1605 a band of Roman Catholics, driven to despair by King James’s persecution of their faith, tried to blow up the English houses of Parliament. The plan was discovered at the last minute, and the conspirators were executed, but the “gunpowder plot” became a symbol among Protestants of the danger Roman Catholicism posed to English Protestantism. In 1689 Parliament drove James II, a Roman Catholic, from the throne of England and replaced him with a Dutch Protestant, William of Orange, and James’s daughter, Mary, William’s wife. They were to rule jointly. A war followed in which Protestants battled Roman Catholics at home and abroad. This was the war that brought the Indians and their French Roman Catholic allies to the doorstep of Salem. Thus the Puritans saw Roman Catholicism as a continuing and powerful threat to Protestantism in England and the survival of Puritanism in New England. They also believed that Roman Catholic priests were in league with the Devil. Reports of priests and Indians worshiping the Devil before they attacked Massachusetts towns regularly made the rounds of the colony. But the problem of spectral evidence remained, for the only ones who could see the witches in their spectral form, andthus say who it was that caused their pain, were the accusers themselves. Here Mather could find no answers in his library. He must leave it and enter the world of ordinary people. No abstract theory or abstruse theology could dictate commonly accepted contemporary notions of the truth of testimony.”

Even while most people had misgivings about the validity and use of supernatural proof, Cotton Mather cited a precedent from 1664 wherein Mathew Hale asserts that such evidence is suitable in cases of necessity. Mather interprets “in particular, the political crisis of the colony and the terrors of war. War against the Devil and war against the popish French and their Indian allies were the same in his mind.” (Ibid., p. 89) Image, “The soul-killing witches that deform the body” shared from University of Virginia SWT Documentary Archive and Transcription Project.