What was the "evidence" against Sarah Good?
Sarah Good is accused by both Tituba and Abigail of being "with the devil." When she is questioned about her alleged relationship with the devil, Tituba claims that he came to her one night and said "I have white people belong to me." She says that when she looked, "there was Goody Good." Abigail then says that she too saw "Sarah Good with the Devil." So the unfortunate Sarah Good becomes the first person denounced as a witch (though the girls soon name several more.) The Proctors learn from Mary, who attended the first day of the trials in Salem, that the "evidence" against Sarah Good was that she could not recite "a single one" of the Ten Commandments after being accused of bewitching several of the girls. In the play, Sarah Good is a poor woman, who "sleeps in ditches," and so there is not much risk in accusing her of witchcraft. In real life, she was a sort of pariah in Salem, and even her young daughter testified against her. As in the play, the evidence against her was "spectral," i.e. based on the visions of her accusers. She was condemned to hang, which she did after giving birth to a child in jail. She never confessed despite having many chances to do so.
When pressed to name names, Sarah Good becomes an easy target for the girls. Like Tituba, she is of a lower social status than the rest of the town. As a ragged, homeless woman, she is often ignored or dismissed as being crazy. Since people in the town already questions Sarah Good's Christian character, the assertion that she works for the devil is easily accepted and not put into question. Once the lower rungs of society are out of the way, the girls turn their claims towards more respected women like Elizabeth Proctor.