which ought to be proved by instruments and witnesses or by the jurors as aforesaid.  In the grand assise no conviction lies for this reason, because when the demandant  offers to prove his allegation, the tenant must defend himself by the duel or the  grand assise, whichever of the two he chooses, and since he voluntarily betakes  himself to the assise he cannot impugn it; if he does so it is evident that he repudiates  his defence, as in the assises, where [if] he puts himself on a jury for some reason, as  explained above, he cannot afterwards repudiate the jurors' verdict,1 [for] if he  should it would be nothing other than to nullify his own proof, and for that reason  no conviction is allowed.2 It is clear that there are assises and juries or inquests, for  trespasses and other things. There are purgations, as where a crime is imputed, or a  delict; purgation will be the proof of innocence. There is also a defence against a  presumption, which is called neither a jury nor an inquest nor a purgation, that is,  where one alleges that something is true and produces suit, defence against the  suit then follows, proof, so to speak, against.the presumption. Several defences are  sometimes admitted against suit, sometimes fewer, as will be explained elsewhere.3  There is one jury which sometimes admits of conviction, as where a jury is taken as  to some matter which touches the lord king and it finds against him; the jurors may  be convicted by others, as before Martin of Pateshull, [the case] of Henry of Monewedene,  who was once in the wardship of the lord king in the time of Hubert de  Burgh.4 A jury or inquest does not admit of conviction, but if their verdict is challenged 5  for some reason certain, emendation follows by a change6 of jurors or their  afforcement.
If there is error in the judgment or the oath.
 If [the jurors] err in their oath or judgment, we must see whether the error is excusable  or the result of gross ignorance, that the punishment may be mitigated. Where7  the matter cannot easily be ascertained except by presumption, as where an agreement  or contract was made secretly, few being present, such error is excusable. But  if it was made publicly and openly, so that everyone in the county knows of it and  only the jurors are ignorant,8 or have doubts, they are not excused of perjury because  this is gross ignorance. If the jurors recite the matter as it is in truth, and afterwards  judge9 the matter according to their recital and err in judgment, the judgment  is foolish rather than false, since they believe such judgment follows from such  facts.10 [But] if the justice pronounces judgment according to their verdict,11 he gives  a false judgment. He ought not, therefore, to follow