Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
It is, however, the evidence that gives the greatest trouble to advocates. Evidence may be given either in writing or orally by witnesses present in court. Documentary evidence is easier to dispose of. For it is likely that the deponent was less ashamed of himself in the presence of a small number of witnesses, and his absence from court is attacked as indicating a lack of confidence. If we cannot call the character of the deponent in question, we may attack the witnesses to his signature.
Further there is always a certain tacit prejudice against documentary evidence, since no one can be forced to give such evidence save of his own free will, whereby he shows that he harbours unfriendly feelings towards the person against whom he bears