CHAPTER XVI. 



THE APPLICATION OF PROBABILITY TO TESTIMONY. 



1. ON the principles which have been adopted in this 

 work, it becomes questionable whether several classes of 

 problems which may seem to have acquired a prescriptive 

 right to admission, will not have to be excluded from the 

 science of Probability. The most important, perhaps, of 

 these refer to what is commonly called the credibility of 

 testimony, estimated either at first hand and directly, or as 

 influencing a juryman, and so reaching us through his 

 sagacity and trustworthiness. Almost every treatise upon 

 the science contains a discussion of the principles according 

 to which credit is to be attached to combinations of the 

 reports of witnesses of various degrees of trustworthiness, or 

 the verdicts of juries consisting of larger or smaller numbers. 

 A great modern mathematician, Poisson, has written an 

 elaborate treatise expressly upon this subject ; whilst a con 

 siderable portion of the works of Laplace, De Morgan, and 

 others, is devoted to an examination of similar enquiries. It 

 would be presumptuous to differ from such authorities as 

 these, except upon the strongest grounds ; but I confess that 

 the extraordinary ingenuity and mathematical ability which 

 have been devoted to these problems, considered as questions 

 in Probability, fails to convince me that they ought to have 

 been so considered. The following are the principal grounds 

 for this opinion. 



