▁discuss ions ▁with ▁colle agues ▁on ▁the ▁subject , ▁testim ony ▁read ▁in ▁prepar ation ▁for ▁testim ony ▁in ▁the ▁case ▁and ▁similar ▁pieces ▁of ▁information ▁not ▁personally ▁known ▁to ▁the ▁expert . ▁ ▁Ch ain ▁of ▁cust ody ▁▁ ▁It ▁is ▁important ▁that ▁expert ▁witness es ▁who ▁handle ▁evidence ▁maintain ▁a ▁proper ▁chain ▁of ▁cust ody ▁such ▁that ▁they ▁are ▁able ▁to ▁authentic ate ▁the ▁evidence , ▁prove ▁that ▁it ▁is ▁what ▁they ▁represent ▁it ▁to ▁be , ▁when ▁test ifying ▁at ▁trial . ▁Most ▁not ably ▁in ▁the ▁context ▁of ▁a ▁criminal ▁pro sec ution , ▁an ▁expert ▁witness es ▁who ▁evalu ates ▁or ▁exam ines ▁an ▁item ▁pert inent ▁to ▁an ▁investigation ▁or ▁case ▁evaluation ▁may ▁add ▁an ▁entry ▁to ▁a ▁“ chain ▁of ▁cust ody ” ▁document , ▁a ▁form ▁that ▁contains ▁the ▁item ' s ▁description , ▁the ▁time ▁and ▁date ▁of ▁release ▁for ▁all ▁prior ▁cust od ians ▁of ▁the ▁item , ▁and ▁the ▁time ▁and ▁date ▁of ▁release ▁to ▁the ▁witness . ▁ ▁We ight ▁of ▁testim ony ▁ ▁In ▁the ▁case ▁of ▁an ▁expert ▁witness , ▁the ▁weight ▁of ▁his / her ▁evidence ▁depends ▁heavily ▁on ▁the ▁foundation ▁support ▁established ▁prior ▁to ▁an ▁opinion ▁being ▁given . ▁Ex amples ▁include ▁educational ▁background , ▁review ▁of ▁scholar ly ▁works , ▁field ▁studies ▁and ▁train ings ▁which ▁all ▁lead ▁up ▁to ▁developing ▁a ▁foundation ▁of ▁knowledge ▁for ▁cred ibility ▁of ▁a ▁testim ony . ▁Before ▁trial , ▁all ▁exper ts ▁must ▁prepare ▁a ▁report ▁summar izing ▁their