Aj^u°S,Pih905m-}  Expert  Testimony.  3 
than  technical  terms,  and  yet  be  expressed  both  clearly  and  ade- 
quately ?  The  only'  way  out  of  the  difficulty  is  not  to  try  to  get  out 
of  it.  Let  us  state  our  technical  position  for  the  record,  as  simply 
as  possible ;  that  is,  in  technical  terms.  We  may  then  explain  in 
untechnical  language  for  the  jury.  One  common  result  of  the  effort 
to  avoid  technical  statements  is  a  multiplication  of  words  from  which 
juries,  even  more  intelligent  than  the  average,  can  gather  no  clear 
idea.  Another  is  an  impossible  simplification  of  a  difficult  problem, 
which  is  consequently,  even  though  a  correct  conclusion  be  reached, 
open  to  just  criticism — a  fortiori  to  captious  criticism.  Just  here 
comes  to  light  one  grave  fault  of  medical  and  chemical  experts. 
We  are  too  prone  to  make  and  to  suggest  that  very  kind  of  captious 
criticism  of  the  testimony  of  an  opposing  witness,  not  for  the  purpose 
of  eliciting  truth,  but  in  order  to  score  a  point  in  the  game.  Such 
tactics  may  be  perfectly  proper  on  the  part  of  an  advocate,  but  not 
on  the  part  of  one  who  professes  to  be  impartially  devoted  to  science. 
And  this  brings  into  view  a  second  difficulty.  Theoretically,  the 
expert  witness  is  an  adviser  of  the  court.  He  is  called  in,  because 
of  his  supposedly  superior  knowledge,  to  help  the  judge  and  jury  to 
understand  the  significance  of  certain  facts  testified  to  by  himself  or 
others,  which  cannot  be  understood  without  such  assistance.  He 
should  have  no  interest  in  the  bearing  of  these  facts  upon  the  verdict 
to  be  rendered.  Was  or  was  not  arsenic  present  in  a  certain  liver 
or  stomach  examined  by  him  ?  Do  or  do  not  certain  post-mortem 
appearances,  or  certain  symptoms  observed  during  life,  indicate  death 
from  poisoning  ?  Is  or  is  not  the  continuous  and  unsuspected  ad- 
ministration of  unknown  quantities  of  boric  acid  or  salicylic  acid  or 
sodium  sulphite  injurious  to  health?  These  and  like  matters  are 
the  subjects  upon  which  he  is  called  to  state  judgments  of  fact  or  to 
express  opinions,  and  in  consequence  to  detail  the  observations  and 
explain  the  reasoning  upon  which  such  judgments  or  opinions  are 
based.  But  his  interest  in  the  matter  should  be  entirely  scientific. 
It  should  be  no  concern  of  his,  as  a  witness,  whether  the  presence 
or  absence  of  arsenic  in  the  tissues  or  other  materials  that  he  has 
examined,  or  the  significance  of  the  symptoms  described,  or  the 
harmfulness  or  harmlessness  of  chemicals  used  as  food  preservatives, 
may  lead  to  the  conviction  or  acquittal  of  any  individual  or  the  gain 
or  loss  of  any  commercial  interest.  His  function  in  court  is  quite 
clear.    It  is  (a)  to  describe  the  methods  and  the  results  cf  his  ex- 
