If a witness said your specter attacked her, proving your body was somewhere else did not answer the accusation.
During the Salem proceedings, magistrates accepted spectral evidence: testimony that the accused person's spirit or spectral shape had appeared to torment an afflicted witness while the accused's physical body was elsewhere. That made an ordinary alibi a poor defense. Showing where your body had been did not directly disprove a claim about a specter acting separately from it.
The theology behind that evidence was not as unanimous as later retellings sometimes make it sound. Judge John Hathorne argued that the Devil could not take an innocent person's shape without that person's consent. Other contemporaries pushed back. Increase Mather and other critics warned that the Devil might assume the appearance of an innocent person, which made spectral identification unsafe as a basis for conviction. The disagreement existed during the crisis itself.
That dispute did not make spectral testimony harmless. As long as magistrates credited an afflicted person's report, the defendant faced an accusation that could not be tested by ordinary physical evidence in the same way as a witnessed act.
Bridget Bishop was the first person tried by the Court of Oyer and Terminer and was hanged on June 10, 1692. Spectral accusations were part of the case against her, alongside a range of other testimony and older allegations. Her case illustrates the role spectral evidence played without reducing the verdict to a single piece of testimony.
Opposition to spectral evidence grew through the summer and fall. Increase Mather's Cases of Conscience Concerning Evil Spirits argued against condemning people on such grounds. Governor William Phips dissolved the Court of Oyer and Terminer in October 1692, and the later Superior Court proceeded without relying on spectral evidence in the same way. Most of the remaining witchcraft cases then ended in acquittal, dismissal, or pardon rather than another wave of executions.
The modern contrast is procedural rather than magical. Courts still hear testimony about events that cannot be replayed, but modern evidence rules give defendants tools for testing witnesses, challenging reliability, and contesting expert claims. Salem's spectral evidence is a stark example of what happens when the system accepts a claim while giving the accused no comparable method to test the thing being claimed.
An alibi works on a body. Salem's accusation did not have to stay in one.