. ▁This ▁test ▁results ▁in ▁uniform ▁dec isions ▁regarding ▁adm iss ibility . ▁In ▁particular , ▁the ▁jud ges ▁in ▁F ry e ▁ruled ▁that : ▁▁ ▁Just ▁when ▁a ▁scientific ▁principle ▁or ▁discovery ▁cross es ▁the ▁line ▁between ▁experimental ▁and ▁demon stra ble ▁stages ▁is ▁difficult ▁to ▁define . ▁Some where ▁in ▁this ▁tw il ight ▁zone ▁the ▁evident ial ▁force ▁of ▁the ▁principle ▁must ▁be ▁recognized , ▁and ▁while ▁courts ▁will ▁go ▁a ▁long ▁way ▁in ▁adm itting ▁expert ▁testim ony ▁dedu ced ▁from ▁a ▁well - recogn ized ▁scientific ▁principle ▁or ▁discovery , ▁the ▁thing ▁from ▁which ▁the ▁dedu ction ▁is ▁made ▁must ▁be ▁sufficiently ▁established ▁to ▁have ▁gained ▁general ▁accept ance ▁in ▁the ▁particular ▁field ▁in ▁which ▁it ▁belongs . ▁ ▁In ▁ 1 9 2 3 , ▁the ▁case ▁of ▁F ry e ▁v . ▁United ▁States ▁instit uted ▁significant ▁change ▁to ▁both ▁criminal ▁and ▁civil ▁law ▁by ▁address ing ▁the ▁use ▁of ▁expert ▁witness ▁testim ony ▁in ▁conj unction ▁with ▁scientific ▁testim ony . ▁In ▁F ry e ▁v . ▁United ▁States , ▁the ▁defense ▁team ▁attempted ▁to ▁introduce ▁both ▁the ▁results ▁of ▁a ▁poly graph ▁test ▁admin ister ed ▁to ▁F ry e ▁to ▁determine ▁F ry e ' s ▁innoc ence ▁as ▁well ▁as ▁the ▁testim ony ▁of ▁an ▁expert ▁witness ▁to ▁verify ▁and ▁explain ▁the ▁results . ▁ ▁However , ▁the ▁court ▁rejected ▁the ▁expert ' s ▁testim ony , ▁r uling ▁that : ▁“ Wh ile ▁courts ▁will ▁go ▁a ▁long ▁way ▁in