VETERINARY JURISPRUDENCE. 
33 
witnesses or as experts or (what is perhaps more frequently the 
ease) both as witnesses of facts and as experts. 
A common witness has to speak as to the matters of fact 
which have come within his personal knowledge. That the ani¬ 
mal he was called to see had sustained severe injuries; that 
poison was present in the stomach of the animal on which he held 
a post-mortem examination, are facts to be proved by scientific 
witnesses; in which, save in the nature of the facts on which he 
has to give evidence, he in no respect differs from an ordinary 
witness. Further, if any fact relating to the case be within the 
personal knowledge of the scientific witness, a subpoena served on 
him to speak to that fact in a court of law is as imperative as when 
served on any other witness. But the skilled or expert witness, 
as he is termed, is called to state his opinions either on facts ob¬ 
served by himself or proved in evidence by others. No witness 
can be compelled to give his opinion in the witness box. The ex¬ 
pert, however wide his experience, cannot be forced to give the 
court the value of his general and special knowledge. The skilled 
witness must form his opinions on the facts he has heard proved. 
Thus expert testimony has been refused because the surgeon had 
not been present during the time that the witnesses were giving 
their evidence, but had based his opinion on the facts submitted 
to him in writing by the attorney. Hence it is not enough for an 
expert to run into court the minute he is wanted; but it is neces¬ 
sary that he should be able to say that his opinions are based on 
the evidence he has himself heard in the witness-box. And here 
a few words may be suggested on the vexed question of expert 
evidence. Nothing is meaner to contemplate than a traffic in evi¬ 
dence, either for gain or notoriety. Hence I would suggest the 
following rule that in my judgment should always guide the 
scientific expert, namely: that no one is justified in giving evi¬ 
dence in support of a case, or in support of part of a case, upon 
which he may be especially retained to give evidence, that he does 
not believe right and true. Any evidence offered by the expert in 
the witness-box should be honestly and truly his scientific belief, 
influenced by reasons as definite and as accnrate as if he was argu¬ 
ing the points in dispute before a scientific tribunal competent to 
judge his arguments and pronounce on his opinions. If the ex- 
