It is a known rule of evidence, that an interest in the matter to be supported by testimony disqualifies a witness; yet Lord Mansfield held, "that _nice_ objections to a remote interest which could not be paid or released, though they held in other cases, were not allowed to disqualify a witness to a will, as parishioners might have [prove?] a devise to the use of the poor of the parish forever." He went still nearer, and his doctrine tends so fully to settle the principles of departure from or adherence to rules of evidence, that your Committee inserts part of the argument at large. "The disability of a witness from interest is very different from a positive incapacity. If a deed must be acknowledged before a judge or notary public, every other person is under a positive incapacity to authenticate it; but objections of interest are deductions from natural reason, and proceed upon a presumption of too great a bias in the mind of the witness, and the public utility of rejecting partial testimony. Presumptions stand no longer than till the contrary is proved. The presumption of bias may be taken off by showing the witness has a [as?] great or a greater interest the other way, or that he has given it up. The presumption of public utility may be answered by showing that it would be very inconvenient, under the particular circumstances, not to receive such testimony. Therefore, from the course of business, necessity, and other reasons of expedience, _numberless exceptions_ are allowed to the _general_ rule."[61]
These being the principles of the latter jurisprudence, the Judges have suffered no positive rule of evidence to counteract those principles. They have even suffered subscribing witnesses to a will which recites the soundness of mind in the testator to be examined to prove his insanity, and then the court received evidence to overturn that testimony and to destroy the credit of those witnesses. They were five in number, who attested to a will and codicil. They were admitted to annul the will they had themselves attested. Objections were taken to the competency of one of the witnesses in support of the will against its subscribing witnesses: 1st, That the witness was an executor in trust, and so liable to actions; 2dly, As having acted under the trust, whereby, if the will were set aside, he would be liable to answer for damages incurred by the sale of the deceased's chambers to a Mr. Frederick. Mr. Frederick offered to submit to a rule to release, for the sake of public justice. Those who maintained the objection cited Siderfin, a reporter of much authority, 51, 115, and 1st Keble, 134. Lord Mansfield, Chief-Justice, did not controvert those authorities; but in the course of obtaining substantial justice he treated both of them with equal contempt, though determined by judges of high reputation. His words are remarkable: "We do not _now_ sit here to take our rules of evidence from Siderfin and Keble." He overruled the objection upon more recent authorities, which, though not in similar circumstances, he considered as within the reason. The Court did not think it necessary that the witness should release, as he had offered to do. "It appeared on this trial," says Justice Blackstone, "that a black conspiracy was formed to set aside the gentleman's will, without any foundation whatever." A prosecution against three of the testamentary witnesses was recommended, who were afterwards convicted of perjury.[62] Had strict formalities with regard to evidence been adhered to in any part of this proceeding, that very black conspiracy would have succeeded, and those black conspirators, instead of receiving the punishment of their crimes, would have enjoyed the reward of their perjury.