Hopkins was a lawyer and the son of James Hopkins, a Puritan clergyman. According to his book The Discovery of Witches (not to be confused with Reginald Scot's book The Discovery of Witchcraft) he began his career as a witch-finder when he allegedly overheard various women discussing their meetings with the Devil in March of 1664, in a village near Colchester. As a result of Hopkins's accusations, nineteen alleged witches were hanged and four more died in prison.
Hopkins was soon travelling over eastern England, claiming truthfully or not to be an official specially commissioned by Parliament to uncover and prosecute witches. His witch-finding career spanned from 1644 to 1646. While torture was technically unlawful in England, he used various methods of browbeating to extract confessions from some of his victims. He used sleep deprivation as a sort of bloodless torture. He also used a "swimming" test to see if the accused would float or sink in water, the theory being that witches had renounced their baptism, so that all water would supernaturally reject them. He also employed "witch prickers" who pricked the accused with knives and special needles, looking for the Devil's mark that was supposed to be dead to all feeling and would not bleed. It was believed that the witch's familiar would drink their blood from the mark.
On the strength of his commission, Hopkins then demanded that the communities he visited pay him for his work. He also sold fetishes he called "witch boxes" that were supposed to protect the households of their owners from sorcery.
Samuel Butler's satire Hudibras commented on Hopkins's activity, saying:
- Has not this present Parliament
- A Lieger to the Devil sent,
- Fully impowr'd to treat about
- Finding revolted witches out
- And has not he, within a year,
- Hang'd threescore of 'em in one shire?
- Some only for not being drown'd,
- And some for sitting above ground,
- Whole days and nights, upon their breeches,
- And feeling pain, were hang'd for witches.
- And some for putting knavish tricks
- Upon green geese and turky-chicks,
- And pigs, that suddenly deceast
- Of griefs unnat'ral, as he guest;
- Who after prov'd himself a witch
- And made a rod for his own breech.
The last line refers to a tradition that disgruntled villagers caught Hopkins and subjected him to his own "swimming" test: he floated, and therefore was hanged for witchcraft himself. However, it is believed by most historians that Hopkins actually died of illness (possibly tuberculosis) in his home. The parish records of Manningtree in Essex record his burial in August of 1647.