Insanity was recognised under English law in the Norman era thus:
“eo quod sensu carent et ratione, non magis quam brutum animal iniuriam facere possunt nec feloniam, cum non multum distent a brutis, secundum quod videri poterit in minore, qui si alium interficeret in minori ætate, iudicium non sustineret.”
(“since they are without sense and reason and can no more commit a tort or a felony than a brute animal, since they are not far removed from brutes, as is evident in the case of a minor, for if he should kill another while under age he would not suffer judgment.”)
Essentially the Normans didn’t recognise insanity as a defence, but as a special circumstance that would allow a jury to render a guilty verdict but to then apply to the King for a pardon. This seems not to have been seriously tested until R v Arnold (1724) 16 St. Tr.704. Arnold shot Lord Onslow, wounding him. Sentenced to death, Lord Onslow secured a reprieve for him to life in prison. Lord Tracey recognised the “wild beast” test:
“A man must be totally deprived of his understanding and memory, so as not to know what he is doing, no more than an infant, a brute, or a wild beast, such a one is never the object of punishment.” Of course the “wild beast” in question actually means a farm animal, not some sort of wild animal.
From this case, R v Ferrers (1760) 16 How St. Tr. 886 saw the House of Lords rule that the Earl was not suffering from an irrestible impulse when he killed his servant. Ferrers was executed and one of his descendants was a 1990s Home Office Minister. R v Hadfield (1800) 27 How St. Tr. determined that a brain-damaged ex-soldier, who shot at George III because he wished to be executed, was suffering from a delusion. Daniel M’Naughten, in 1843, shot Robert Peel’s secretary, believing him to be the Prime Minister in person, conspiring against M’Naughten, the Lords’ “rules in M’Naughten’s case” becoming the basis of common law on insanity, only slightly revised.
So what of historical cases within or close to our period?
1) Edward Earl of Warwick, imprisoned by Henry “Tudor” within days of his accession, only seems to have left the Tower three times: for display in 1487, for trial in 1499 and for his execution that November. It was said that he “could not tell a goose from a capon”, presumably as a result of his seclusion, suggesting that he may have fallen under the Norman law.
2) “Perkin Warbeck”, who might have been Richard of Shrewsbury or a conscious fraud. Alternatively, he may have been a non-Royal individual who was under the delusion that he was Richard of Shrewsbury. As we just don’t know who he was, his sanity would depend on that.
3) Jane Parker, Viscountess Rochford, executed in 1542 for participating in Katherine Howard’s treason. She was attainted and widely recognised to have been insane.
Evidently, the “Tudors” were no respectors of English common law.