ired ▁guns ." ▁ ▁Qual ifications ▁of ▁expert ▁witness es ▁ ▁An ▁expert ▁witness ▁at ▁the ▁time ▁of ▁trial ▁is ▁qualified ▁by ▁the ▁court ▁and ▁must ▁be ▁re - qual ified ▁each ▁time ▁that ▁person ▁comes ▁to ▁trial ▁for ▁the ▁offering ▁of ▁opinions . ▁The ▁qual ification ▁is ▁given ▁by ▁each ▁trial ▁judge ▁and ▁takes ▁place ▁regardless ▁of ▁prior ▁appearances ▁by ▁a ▁particular ▁expert ▁witness . ▁Ex pert ▁witness es ▁are ▁those ▁who ▁the ▁court ▁has ▁de emed ▁qualified ▁to ▁speak ▁on ▁a ▁topic ▁to ▁provide ▁background ▁to ▁anyone ▁on ▁a ▁lay ▁j ury . ▁ ▁D ut ies ▁of ▁exper ts ▁in ▁United ▁States ▁Cour ts ▁In ▁high ▁st akes ▁cases ▁multiple ▁exper ts , ▁in ▁multiple ▁topics , ▁are ▁often ▁retained ▁by ▁each ▁party . ▁Although ▁it ▁is ▁still ▁relatively ▁rare , ▁the ▁court ▁itself ▁may ▁also ▁retain ▁its ▁own ▁independent ▁expert . ▁In ▁all ▁cases , ▁fe es ▁paid ▁to ▁an ▁expert ▁may ▁not ▁be ▁cont ing ent ▁on ▁the ▁outcome ▁of ▁the ▁case . ▁ ▁Ex pert ▁evidence ▁is ▁often ▁the ▁most ▁important ▁component ▁of ▁many ▁civil ▁and ▁criminal ▁cases ▁today . ▁F inger print ▁exam ination , ▁blood ▁analysis , ▁DNA ▁finger print ing , ▁and ▁for ens ic ▁fire arm ▁exam ination ▁are ▁common ▁kinds ▁of ▁expert ▁evidence ▁heard ▁in ▁serious ▁criminal ▁cases . ▁In ▁civil ▁cases , ▁the ▁work ▁of ▁accident ▁analysis , ▁for ens ic ▁engine ers , ▁and ▁for ens ic ▁account ants ▁is ▁usually ▁important , ▁the ▁latter ▁to ▁assess ▁dam ages ▁and