SALMON v. CLAGETT.—3 BLAND. 165

to the condition of a mere disinterested witness, his testimony, if
required, may be taken as such. Richardson v. Hulbert, 1 Anstr.
65; Cartwright v. Hateley, 1 Ves. Jun. 292; Fenton v. Hughes, 7
Ves. 287.

Now we have seen, that the reason why the defendant may be
compelled to answer as the bill requires, is, that the plaintiff is
entitled to his evidence, either because he cannot otherwise prove
his case, or to save expense. But, no man can be compelled to
criminate himself; nor shall any attorney be permitted to divulge
the secrets of his client. These are fundamental axioms restrictive
of the right to call for testimony in any manner or form whatever.
Inquiries, made in violation of these axioms, are unlawful; and,
consequently, cannot be answered; since the submission of a de-
fendant to answer must be understood to be qualified by restric-
tions that are applicable, indiscriminately, to all modes and forms
of calling for evidence. The plaintiff has a right to a full answer
to save expense. But he cannot be thus indulged in the saving of
expense to himself to the injury of another disinterested and inno-
cent person. Nemo debet locupletari ex alterius incommodo. A
plaintiff shall not be permitted to burthen a keeper of public re-
cords with the expense of making out, and producing copies which
any one may obtain on paying the legal fees; nor shall a plaintiff
be permitted to save expense to himself by making a mere disin-
terested witness a party and burthening him with the expense in-
cident to that character.

But these allegations can never be advanced in avoidance, or
put in issue as a defence; because they create no defence. Brown-
sword v. Edwards, 2 Ves. 246. They are grounded merely on the
privilege of the defendant or his client; and on the right, of every
oue to disengage himself at once from a controversy with which he
cannot be encumbered as an interested party, either in his public
or private capacity; and consequently they are qualifications; but
cannot be considered as exceptions from the general rule; since
that which must always be, and necessarily is assumed as an ad-
mitted proposition, without which a rule cannot be applicable to
any case, cannot, with propriety, be considered as, in any respect,
an exception to such rule. * The object of the interrogate-
ries of the bill is, lawfully to obtain answers thereto, for the 147
purpose of using them as evidence applicable to a case of which the
Court has jurisdiction. But these disclosures may be very injuri-
ous or destructive to the interests of the defendant; and he may
be able to shew, that, in equity, he is not and ought not to be
bound to make any discovery whatever. A plea is exactly calcu-
lated for this purpose. Whatever shews there is no right which
can be made the foundation of a suit, may constitute the subject
of a plea. One of its main objects is to advance such new matter
as has not been shewn or relied on by the plaintiff, as will preclude