[1] From a family settled in North Wales, he was eldest son of William Jones of Castellmarch, Carnarvonshire, by Margaret, daughter of Humphry Wynn ap Meredith of Hyssoilfarch.

He was Lent reader of the inn in 1616 and was made a serjeant and knight on 14 March 1617; on 13 May of the same year he was appointed Lord Chief Justice of the King's Bench for Ireland, in succession to Sir John Denham, who had been transferred to the English court of exchequer.

On 25 September 1621, he was appointed a judge of the Court of Common Pleas, and on 20 March 1622 was selected as a member of a commission to go to Ireland.

He complained to Lionel Cranfield, 1st Earl of Middlesex that the commissioners refused to recognise him as a judge, or entitled to any precedence on the commission, and that he was placed junior on it.

[2] Thomas Hearne in his Curious Discourses prints a paper by Jones on the early Britons, read before the Society of Antiquaries in Elizabeth I's reign, and calls him a person of learning in British antiquities.