4 
Expert  lestimony. 
f Am.  Jour.  Pharui. 
I     January,  1905. 
animations ;  to  state  the  conclusions  that  his  study  and  obser- 
vation in  general  enable  him  to  draw  rom  a  given  set  of  facts  ob- 
served and  described  by  him  or  testified  to  by  others  ;  (r)  to  enlighten 
the  court  as  to  matters  of  scientific  knowledge  relevant  to  the  issues 
presented,  but  not  dependent  upon  any  testimony  as  to  fact  given  in 
the  special  cause  at  trial.  Beyond  that  his  testimony,  his  advicev 
his  interest,  should  not  go. 
Under  present  methods,  however,  the  expert  witness  is  not  sum- 
moned  in  his  theoretical  capacity  of  impartial  teacher  and  adviser. 
He  is  called  apparently,  and  often  in  reality,  as  a  partisan  and  an 
advocate.  Indeed,  whatever  his  own  view  may  be  as  to  his  relation 
to  the  case,  he  is  usually  regarded  and  treated  as  a  partisan  and 
advocate  by  judge,  jury,  lawyers,  spectators  and  newspapers.  How 
often  do  we  read  in  great  headlines  of  the  "  Battle  of  the  Experts  !  " 
How  often  is  the  speculation  heard,  privately  or  publicly,  as  to 
whether  the  prosecution  or  the  defense  will  "  get  Dr.  A.,"  with  the 
implication  that  the  other  side  will  then  necessarily  "  get  Dr.  B.," 
and  that  Drs.  A.  and  B.  will,  of  equal  necessity,  express  in  court 
opposite  opinions  on  the  same  facts. 
There  is  unquestionably  a  legitimate  field  of  work  for  the  scientific 
or  "  expert  "  advocate  ;  but  it  is  tjy  the  side  of  counsel,  not  on  the 
witness  stand.  As  witness,  one  is  bound  by  his  oath  and  by  his  duty 
to  the  court  and  to  the  State  to  endeavor  to  assist  judge  and  jury 
to  reach  correct  conclusions,  without  reference  to  the  effect  of  those 
conclusions  upon  the  verdict  to  be  rendered.  He  is  to  distort 
nothing,  magnify  nothing,  minimize  nothing  ;  assert  as  positive 
nothing  doubtful,  throw  doubt  upon  nothing  certain ;  introduce 
nothing  irrelevant,  suppress  nothing  material ;  give  utterance  to  no 
statement  of  fact,  advance  no  theory,  that  he  would  shrink  from 
defending  before  a  learned  society.  But  as  advocate,  one  may 
properly  consider  the  bearing  of  testimony  upon  the  verdict  and 
endeavor  to  have  judge  and  jury  impressed  with  the  especial  im- 
portance of  those  facts  and  theories  making  for  his  side  of  the  case, 
and  with  the  doubtfulness  and  unimportance  of  those  making  for 
the  opposing  side.  The  functions  of  the  witness  and  of  the  advo- 
cate should  therefore  never  be  united  in  the  same  person.  Human 
nature  being  what  it  is,  however,  our  present  methods  tend  to  im- 
bue expert  witnesses  with  somewhat  of  the  advocate's  spirit.  Some 
do  not  realize  this  tendency  ;  others,  despite  their  effort  to  avoid 
