The Collaborative International Dictionary of English v.0.48:

deaf and dumb \deaf and dumb\, deaf-and-dumb \deaf-and-dumb\adj.
   both deaf and unable to speak; without the sense of hearing
   or the faculty of speech. Same as Deaf-mute.
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Dumb \Dumb\, a. [AS. dumb; akin to D. dom stupid, dumb, Sw.
   dumb, Goth. dumbs; cf. Gr. ? blind. See Deaf, and cf.
   Dummy.]
   1. Destitute of the power of speech; unable; to utter
      articulate sounds; as, the dumb brutes.
      [1913 Webster]

            To unloose the very tongues even of dumb creatures.
                                                  --Hooker.
      [1913 Webster]

   2. Not willing to speak; mute; silent; not speaking; not
      accompanied by words; as, dumb show.
      [1913 Webster]

            This spirit, dumb to us, will speak to him. --Shak.
      [1913 Webster]

            To pierce into the dumb past.         -- J. C.
                                                  Shairp.
      [1913 Webster]

   3. Lacking brightness or clearness, as a color. [R.]
      [1913 Webster]

            Her stern was painted of a dumb white or dun color.
                                                  --De Foe.
      [1913 Webster]

   Deaf and dumb. See Deaf-mute.

   Dumb ague, or Dumb chill, a form of intermittent fever
      which has no well-defined "chill." [U.S.]

   Dumb animal, any animal except man; -- usually restricted
      to a domestic quadruped; -- so called in contradistinction
      to man, who is a "speaking animal."

   Dumb cake, a cake made in silence by girls on St. Mark's
      eve, with certain mystic ceremonies, to discover their
      future husbands. --Halliwell.

   Dumb cane (Bot.), a west Indian plant of the Arum family
      (Dieffenbachia seguina), which, when chewed, causes the
      tongue to swell, and destroys temporarily the power of
      speech.

   Dumb crambo. See under crambo.

   Dumb show.
      (a) Formerly, a part of a dramatic representation, shown
          in pantomime. "Inexplicable dumb shows and noise."
          --Shak.
      (b) Signs and gestures without words; as, to tell a story
          in dumb show.

   To strike dumb, to confound; to astonish; to render silent
      by astonishment; or, it may be, to deprive of the power of
      speech.

   Syn: Silent; speechless; noiseless. See Mute.
        [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

DEAF AND DUMB. No definition is requisite, as the words are sufficiently
known. A person deaf and dumb is doli capax but with such persons who have
not been educated, and who cannot communicate, their ideas in writing, a
difficulty sometimes arises on the trial.
     2. A case occurred of a woman, deaf and dumb, who was charged with a
crime. She was brought to the bar, and the indictment was then read to her,
and the question, in the usual form, was put, guilty or not guilty ? The
counsel for the prisoner then rose, and stated that he could not allow his
client to plead to the indictment, until it was explained to her that she
was at liberty to plead guilty or not guilty. This attempted to be done, but
was found impossible, and she was discharged from the bar "simpliciter."
     3. A person, deaf and dumb, may be examined as a witness, provided he
can be sworn, that is, if he is capable of understanding the terms of the
oath, and assents to it and if, after he is sworn, he can convey his ideas,
with or without an interpreter, to the court and jury. Phil., Ev. 14.