10 
Expert  Testimony. 
/Am.  Jour.  Pharm. 
January,  1905. 
them  on  cross-examination;  and  the  whole  truth  thus  failing  to  be 
brought  out,  a  false  impression  would  be  left  on  the  minds  of  the 
jurymen.  Again,  the  widespread  distribution  of  arsenic  in  nature 
and  art  might  be  testified  to  by  expert  witnesses,  truthfully  in  a 
sense,  and  yet  partially,  and  therefore  untruthfully  in  the  large 
sense.  By  such  testimony  a  jury  might  easily  be  misled  as  to  the 
real  significance  of  the  facts.  For  this  is  all  matter  of  fact,  not  of 
opinion,  whether  or  not  it  be  matter  of  personal  observation. 
While,  therefore,  the  mere  circumstance  that  a  witness  has  not  per- 
sonally observed  the  fact  of  science  concerning  which  he  is  ques- 
tioned should  not  bar  his  testimony,  it  does  seem  that  courts  should 
exercise  considerable  caution  as  to  the  admission  of  such  testimony, 
and  might  rightfully  insist,  first,  that  its  relevancy  to  the  special 
cause  at  trial  be  established  ;  secondly,  that  the  witness  should  be 
required  to  affirm  his  familiarity  with  all  the  pertinent  details  of  the 
special  facts  to  be  testified  to,  and,  furthermore,  be  required  to  state 
them,  even  in  the  absence  of  cross-examination.  Failure  on  the 
part  of  a  witness  to  make  such  full  statement  should  then  be  con- 
sidered sufficient  reason,  if  shown,  to  throw  out  all  his  testimony, 
This  rule  would  at  least  tend  to  discourage  witnesses  from  giving 
partial  and  misleading  testimony. 
Another  order  of  testimony  given  by  experts  relates  to  matters 
purely  of  opinion.  Here  the  position  becomes  more  difficult  both 
for  court  and  witness. 
A  pharmacist  testifying  as  a  matter  of  chemical  fact  that  he  has 
found  a  certain  quantity  of  arsenic  or  strychnin  in  a  human  body, 
may  be  asked  whether  it  is  sufficient  to  kill  or  indicates  that  there 
has  been  in  the  body  at  any  time  sufficient  to  kill  ?  The  least  quan- 
tity of  arsenic  or  any  other  poison  necessary  to  kill  a  human  being 
should  be  a  matter  of  fact ;  it  is,  however,  for  many  reasons,  one  of 
opinion.  In  the  first  place,  the  experiment  has  never  been  made 
under  rigorous  conditions.  In  the  second  place,  in  most,  if  not  all 
of  the  recorded  cases  of  poisoning,  alike  in  those  attended  with  re- 
covery and  those  ending  fatally,  either  the  exact  quantity  taken  is 
unknown,  or  it  is  so  large  that  no  estimate  of  a  minimum  lethal  dose 
can  be  based  upon  it — while  in  cases  of  recovery  from  large  doses 
there  has  often  been  evacuant,  antidotal,  or  other  treatment.  In 
the  third  place  the  individual  variations  in  responses  to  drugs  of  all 
kinds  are  great.    Moreover,  the  hearsay  element  must  be  large  in 
