Testes ponderantur, non numerantur
Defined in 2 dictionaries — Ballentine's (1916), Black's (1910)
Ballentine's Law Dictionary
James A. Ballentine · 1916
Witnesses are weighed, not counted.
Black's Law Dictionary
Henry Campbell Black, M.A. · 1910
Witnesses are weighed, not numbered. That is, in case of a conflict of evidence, the truth is to be sought by weighing the credibility of the respective witnesses, not by the mere numerical preponderance on one side or the other.