Imprisoned for his lack of sympathy to Catholicism and subjected to intense pressure to convert, in a disturbed state of mind he committed suicide by drowning.

The resulting lawsuit of Hales v. Petit is considered to be a source of the gravediggers' dialogue after Ophelia drowns herself in Shakespeare's play Hamlet.

However, in 1553 he was one of three judges who refused to seal the document by which John Dudley, 1st Duke of Northumberland attempted to settle the crown on the Protestant Lady Jane Grey.

In October 1553 the Queen renewed his post as a Justice of the Common Pleas but the Lord Chancellor, the reinstated Bishop Gardiner, refused to take his oath and instead sent him to jail.

By then, however, his mental condition was so unsettled that on 4 August of that year, while staying at Thanington near Canterbury with his nephew, he drowned himself by lying face down in a shallow stream.

[10][11] In 1558 his widow instigated legal proceedings against Cyriac Petit to recover a lease of land in Graveney marsh which had been made in 1551 to herself and her late husband.

Shakespearean commentator John Hawkins (1773) noted[14] the similarity in phrasing between Plowden's report of the case: Walsh said that the Act consists of three Parts.