In a death row appeal soon to come before the US Supreme Court, Robert McCoy will ask whether it is unconstitutional for defence counsel to tell a jury that his client is guilty, in defiance of the accused’s express instructions that he is innocent. McCoy’s lawyer did this in his 2011 murder trial in Louisiana, in a misguided attempt to get his client life imprisonment instead of the death penalty. The lawyer had rejected the opinions of psychiatrists who had found McCoy fit for trial, believing that he was insane and delusional, and that the only way to save his life was to tell the jury he had committed the three murders with which he was charged, in the hope of leniency. The jury promptly convicted McCoy of first-degree murder, and he was sentenced to death.

Until 1836, persons accused of felonies (more serious crimes) in England had no right to be represented at their trial (though some were, if they could pay for an advocate and persuade an accommodating judge). The rationale was given by William Hawkins, an early 18th-century authority on criminal law:

It requires no manner of Skill to make a plain and honest Defence, which ... is always the best; the Simplicity and Innocence, artless and ingenuous Behaviour of one whose Conscience acquits him, having something in it more moving and convincing than the highest Eloquence of a Person speaking in a cause not their own.

In the United States, criminal defendants gained a right to trial counsel in 1789, with the Sixth Amendment to the Constitution, the interpretation of which is at issue in McCoy’s case. The Originalists among the Supreme Court justices may want to know how things stood in England at that time. They must decide how far the lawyer can go without or in spite of the client’s express instruction.

The way the Supreme Court rules in McCoy v. Louisiana may have implications for Donald Trump and his attorney John Dowd, who claimed authorship of the tweet that appeared to fix the president with far more knowledge of the former national security adviser Michael Flynn’s misdeeds than he had previously admitted. Trump is not (yet) on trial, and he hastily disavowed the tweet. It’s hard to tell how much trouble it will get either Trump or Dowd into, but part of the answer may come from a man on death row in Louisiana.