▁or ▁otherwise " ▁so ▁long ▁as : ▁"( 1 ) ▁the ▁testim ony ▁is ▁based ▁upon ▁sufficient ▁facts ▁or ▁data , ▁( 2 ) ▁the ▁testim ony ▁is ▁the ▁product ▁of ▁reliable ▁principles ▁and ▁methods , ▁and ▁( 3 ) ▁the ▁witness ▁has ▁applied ▁the ▁principles ▁and ▁methods ▁reli ably ▁to ▁the ▁facts ▁of ▁the ▁case ." ▁ ▁Although ▁exper ts ▁can ▁test ify ▁in ▁any ▁case ▁in ▁which ▁their ▁expert ise ▁is ▁relevant , ▁criminal ▁cases ▁are ▁more ▁likely ▁to ▁use ▁for ens ic ▁scient ists ▁or ▁for ens ic ▁psych olog ists , ▁whereas ▁civil ▁cases , ▁such ▁as ▁personal ▁injury , ▁may ▁use ▁for ens ic ▁engine ers , ▁for ens ic ▁account ants , ▁employ ment ▁consult ants ▁or ▁care ▁exper ts . ▁Senior ▁phys icians ▁– ▁UK , ▁Ireland , ▁and ▁Commonwealth ▁consult ants , ▁U . S . ▁att ending ▁phys icians ▁– ▁are ▁frequently ▁used ▁in ▁both ▁the ▁civil ▁and ▁criminal ▁courts . ▁ ▁The ▁Federal ▁Court ▁of ▁Australia ▁has ▁issued ▁gu idel ines ▁for ▁exper ts ▁appearing ▁in ▁Australian ▁courts . ▁This ▁covers ▁the ▁format ▁of ▁the ▁expert ' s ▁written ▁testim ony ▁as ▁well ▁as ▁their ▁behaviour ▁in ▁court . ▁Similar ▁procedures ▁apply ▁in ▁non - court ▁for ums , ▁such ▁as ▁the ▁Australian ▁Human ▁Rights ▁and ▁Equ al ▁O pport unity ▁Commission . ▁ ▁Edu c ating ▁witness ▁ ▁The ▁educ ating ▁witness ▁teach es ▁the ▁fact - find er ▁( j ury ▁or , ▁in ▁a ▁ben ch ▁trial , ▁judge )