If the charter is adequate and genuine, the exception that it was made while the donor  was not of sound mind or sound memory may be urged against it, which may be  proved by the witnesses named in the charter and by the country. How this ought to  be proved will be explained more fully below in the title on warranty of charter.1
When one is not bound to warrant.
 The warrantor may also except against the tenant who vouched that though the  charter of feoffment is good the gift is invalid, because the donee who proffers the  charter, or his ancestor to whom the gift was said to be made, never had seisin of the  land during the donor's lifetime,2 only by intrusion after his death, because of which  the vouchee intends to claim it in demesne on the seisin of his ancestor, who died  seised thereof as of fee.
The exception that the donor was never in seisin.
 He may also except that [his] ancestor, who is alleged to have made the gift, was never  in such seisin of it that he could make a gift. A charter, which is only the vestment of a  gift, may be good and the gift bad for want of seisin, and conversely the gift may be  good and the charter bad,3 and sometimes both may be bad and thus both void. Hence  if a charter of gift is put forward, the warrantor must deny both, that is, the charter  and the gift, and thus the tenant must prove both, because of the copulative put between  them. Hence if he fails in the proof of one, he ought to be treated as if he has  failed in the proof of both. For it is not enough to prove the charter valid if the gift is  incomplete. He who admits the gift is bound to warrant, though he may show that the  charter is defective or forged, because a gift may be valid though no charter is made,  as [in the roll] of the eyre of William of Ralegh in the county of Buckingham, [the  case] of Alice de Roche.4 Though a gift is invalid at the outset for want of seisin, it  may later be cured by the heir, as where, when the donee is in seisin in some way, and  after the right has descended to the heir,5 he acknowledges his father's charter and  gift and takes the donee's homage, or confirms his father's gift; he cannot claim that  land in demesne but is bound to warrant it against others, as [in the roll] of the eyre of  Martin of Pateshull and his companions in divers counties after