116 ESSENTIALS OF VETERINARY LAW 
age medical witness appear far more ignorant than 
he really is. One well posted witness is worth 
several men with ‘‘reputations,’’? but who show 
inexactness in examination. Where a witness 
guesses at an answer he is very likely to greatly 
weaken the force of his testimony. If he does not 
know he should say so, and then when he says a 
thing it will be presumed that he knows that which 
he pretends to know. 
It often happens that a lawyer gets from tlie 
witness an admission of a certain fact, and then 
asks if some other fact is not dependent upon the 
acceptance of the first. While such a sequence 
might be common, or very usual, it is unsafe for 
the witness to give an unqualified approval. In 
such cases the expression ‘‘Not necessarily’’ 
proves often exceedingly valuable. 
87. Expert Testimony. Justice frequently de- 
mands that special evidence be given, of a techni- 
cal nature, and that the opinion of those competent 
to decide as to technical points be given to the jury 
to enable the latter to arrive at an equable deci- 
sion. Not all technical witnesses, testifying as to 
professional matters, are the givers of ‘‘expert 
testimony,’’ irrespective of their competency to 
give such expert judgments or opinions. ‘‘The 
value of professional services is not a question of 
science to be proved by expert testimony.’’ 4® Such 
a matter is a question of fact, to be determined by 
usage and circumstances. Therefore, it has been 
held that a person who is not an attorney is com- 
petent to prove the value of an attorney’s serv- 
45 Walker v. Cook, 33 Il. 
App. 561. 
