Charles was moved to Hurst Castle at the end of 1648, and thereafter to Windsor Castle. In January 1649, the Rump House of Commons indicted him on a charge of treason, which was rejected by the House of Lords. The idea of trying a king was a novel one. The Chief Justices of the three common law courts of England – Henry Rolle, Oliver St John and John Wilde – all opposed the indictment as unlawful.
The Rump Commons declared itself capable of legislating alone, House of Lords passed a bill creating a separate court for Charles’s trial, and declared the bill an act without the need for royal assent. The High Court of Justice established by the Act consisted of 135 commissioners, but many either refused to serve or chose to stay away. Only 68 (all firm Parliamentarians) attended Charles’s trial on charges of high treason and “other high crimes” that began on January 20, 1649 in Westminster Hall. John Bradshaw acted as President of the Court, and the prosecution was led by the Solicitor General, John Cook.
Charles was accused of treason against England by using his power to pursue his personal interest rather than the good of the country. The charge stated that he, “for accomplishment of such his designs, and for the protecting of himself and his adherents in his and their wicked practices, to the same ends hath traitorously and maliciously levied war against the present Parliament, and the people therein represented”, and that the “wicked designs, wars, and evil practices of him, the said Charles Stuart, have been, and are carried on for the advancement and upholding of a personal interest of will, power, and pretended prerogative to himself and his family, against the public interest, common right, liberty, justice, and peace of the people of this nation.
Reflecting the modern concept of command responsibility, the indictment held him “guilty of all the treasons, murders, rapines, burnings, spoils, desolations, damages and mischiefs to this nation, acted and committed in the said wars, or occasioned thereby.” An estimated 300,000 people, or 6% of the population, died during the war.
Over the first three days of the trial, whenever Charles was asked to plead, he refused stating his objection with the words: “I would know by what power I am called hither, by what lawful authority…?” He claimed that no court had jurisdiction over a monarch, that his own authority to rule had been given to him by God and by the traditional laws of England, and that the power wielded by those trying him was only that of force of arms. Charles insisted that the trial was illegal, explaining that,
no earthly power can justly call me (who am your King) in question as a delinquent … this day’s proceeding cannot be warranted by God’s laws; for, on the contrary, the authority of obedience unto Kings is clearly warranted, and strictly commanded in both the Old and New Testament … for the law of this land, I am no less confident, that no learned lawyer will affirm that an impeachment can lie against the King, they all going in his name: and one of their maxims is, that the King can do no wrong … the higher House is totally excluded; and for the House of Commons, it is too well known that the major part of them are detained or deterred from sitting … the arms I took up were only to defend the fundamental laws of this kingdom against those who have supposed my power hath totally changed the ancient government.
The court, by contrast, challenged the doctrine of sovereign immunity and proposed that “the King of England was not a person, but an office whose every occupant was entrusted with a limited power to govern ‘by and according to the laws of the land and not otherwise’.
At the end of the third day, Charles was removed from the court, which then heard over 30 witnesses against the king in his absence over the next two days, and on 26 January condemned him to death. The following day, the king was brought before a public session of the commission, declared guilty, and was formally sentenced to death. Fifty-nine of the commissioners signed Charles’s death warrant.