▁modern ▁rules ▁on ▁expert ▁testim ony . ▁ ▁Ro le ▁of ▁expert ▁witness es ▁Ex pert ▁witness es ▁are ▁called ▁upon ▁in ▁the ▁court ▁system ▁to ▁serve ▁as ▁an ▁objective ▁party ▁to ▁the ▁law suit ▁and ▁never ▁function ▁as ▁an ▁advoc ate ▁for ▁one ▁side ▁or ▁the ▁other . ▁Ex pert ▁witness es ▁are ▁present ▁in ▁lit ig ation ▁to ▁explain ▁complicated ▁scientific ▁issues , ▁not ▁to ▁influence ▁the ▁j ury ▁or ▁judge ▁with ▁fer vor . ▁The ▁main ▁respons ib ilities ▁of ▁expert ▁witness es ▁are ▁to ▁evaluate ▁potential ▁problems , ▁defect s , ▁def ic ien cies , ▁or ▁errors ▁only ▁when ▁able ▁to ▁fully ▁appreciate ▁a ▁process ▁or ▁system . ▁Ex pert ▁witness es ▁are ▁oblig ated ▁to ▁study ▁the ▁processes ▁prior ▁to ▁making ▁a ▁survey ▁or ▁post p one ▁the ▁assignment ▁prior ▁to ▁potentially ▁missing ▁the ▁target ▁due ▁to ▁lack ▁of ▁specific ▁condition ▁understanding . ▁They ▁are ▁called ▁to ▁test ify ▁under ▁the ▁assumption ▁with ▁all ▁the ▁prepar ation ▁required ▁for ▁a ▁compet ent ▁evaluation ▁of ▁the ▁process . ▁ ▁Typ ically , ▁exper ts ▁are ▁re lied ▁on ▁for ▁opinions ▁on ▁sever ity ▁of ▁injury , ▁degree ▁of ▁san ity , ▁cause ▁of ▁failure ▁in ▁a ▁machine ▁or ▁other ▁device , ▁loss ▁of ▁ear nings ▁and ▁associated ▁benefits , ▁care ▁costs , ▁and ▁the ▁like . ▁In ▁an ▁intellectual ▁property ▁case ▁an ▁expert ▁may ▁be ▁shown ▁two ▁music ▁scores , ▁book ▁texts , ▁or ▁circuit ▁bo ards ▁and ▁asked ▁to ▁as certain ▁their ▁degree ▁of ▁similarity . ▁In