6 
Expert  Testimony. 
f  Am.  Jour.  Pharm, 
i     January,  1905. 
not  more  dubious,  than  ordinary  judgments;  for  example,  that  of  a 
navigator  as  to  the  position  of  his  ship,  or  of  a  surveyor  as  to  the 
dimensions  of  a  certain  plot  of  ground,  or  of  a  skilled  weigher  as  to 
the  number  of  pounds  contained  in  a  heap  of  coal.  The  differences 
that  may  exist  among  these  various  judgments  are  not  those  of 
kind,  but  merely  ot  degrees  of  complexity.  Such  judgments  may 
be  mistaken;  but  that,  while  it  subjects  them  to  correction,  does 
not  remove  them  to  the  category  of  opinions — unless  the  term 
opinion  be  extended  to  include  every  mental  operation  in  the  nature 
of  a  judgment. 
Testimony  concerning  chemical  analysis  and  its  results  is  properly 
to  be  subjected  to  criticism  as  to  the  pertinency,  correctness,  skill, 
and  accuracy  of  the  manipulations  and  as  to  their  conclusiveness  ; 
but  such  criticism  deals  with  fact,  and  must  be  kept  within  due 
bounds.  It  is  perfectly  proper  to  point  out,  for  example,  that  in  the 
attempted  identification  of  poisons,  a  careless  observer  may  mistake 
antimony  for  arsenic;  but  it  is  misleading — and  a  competent  chemist 
must  consider  it  deliberately  so — to  attempt  to  make  a  jury  believe 
that  discrimination  between  arsenic  and  antimony  is  at  all  uncertain 
when  the  right  tests  have  been  made  with  due  care  and  intelligence 
It  is  not  in  any  degree  a  matter  of  opinion  subject  to  debate  and 
dispute,  but  an  acknowledged  fact  of  science.  No  expert  should 
lend  himself  to  a  pettifogging  practice  of  the  nature  described. 
Again,  it  is  proper  to  point  out  and  inquire  about  all  sources  of 
error  in  manipulation;  but  undue  insistence  upon  widespread  con- 
tamination of  vessels  and  reagents  with,  for  example,  arsenic,  can 
be  considered  only  captious  criticism  in  the  presence  of  statements 
that  due  care  has  been  taken  by  blank  tests  and  otherwise  to  exclude 
that  source  of  error  and  when  amounts  have  been  found  not  to  be 
accounted  for  even  approximately  by  these  common  contaminations. 
I  have  elsewhere  suggested  that  important  examinations  by  official 
analysts  should  be  made  in  the  presence  of  experts  representing  the 
other  side ;  or  that  both  sides  should,  in  cases  in  which  this  method 
is  possible,  be  permitted  to  have  analyses  made  by  their  respective 
experts.  The  further  suggestion  was  also  made  that  analysts 
should  be  required  to  be  preserve  the  results  of  final  and  decisive 
tests  for  exhibition  and  criticism  in  court.  Such  procedures  would 
go  far,  I  think,  to  avert  the  sort  of  criticism  here  deprecated  and  also 
to  guard  against  incompetence,  carelessness  or  error,  in  official  or 
partisan  analysis. 
