about one to four
`` I myself took a print of the prisoner 's thumb -- having first obtained the prisoner 's consent after warning him that the print would be used in evidence against him -- and I compared that print with the mark on this paper . The comparison was made with the greatest care and by the most approved method , point by point and detail by detail , and the two prints were found to be identical in every respect . `` Now it has been proved by exact calculations -- which calculations I have personally verified -- that the chance that the print of a single finger of any given person will be exactly like the print of the same finger of any other given person is as one to sixty-four thousand millions . That is to say that , since the number of the entire human race is about sixteen thousand millions , the chance is about one to four that the print of a single finger of any one person will be identical with that of the same finger of any other member of the human race . `` It has been said by a great authority -- and I entirely agree with the statement -- that a complete , or nearly complete , accordance between two prints of a single finger affords evidence requiring no corroboration that the persons from whom they were made are the same . `` Now , these calculations apply to the prints of ordinary and normal fingers or thumbs . But the thumb from which these prints were taken is not ordinary or normal .