▁form ▁and ▁to ▁authentic ate ▁it ▁for ▁adm iss ibility ▁in ▁disput es ▁and ▁in ▁court . ▁ ▁UK ▁A CP O ▁gu idel ines ▁In ▁the ▁United ▁Kingdom , ▁exam in ers ▁usually ▁follow ▁gu idel ines ▁issued ▁by ▁the ▁Association ▁of ▁Chief ▁Police ▁Offic ers ▁( AC PO ) ▁for ▁the ▁authentication ▁and ▁integrity ▁of ▁evidence . ▁They ▁were ▁updated ▁to ▁Version ▁ 5 ▁in ▁October ▁ 2 0 1 1 ▁when ▁computer ▁based ▁evidence ▁was ▁replaced ▁with ▁digital ▁evidence ▁reflect ing ▁the ▁development ▁of ▁investig ating ▁information ▁security ▁inc idents ▁in ▁a ▁wider ▁context . ▁The ▁gu idel ines ▁consist ▁of ▁four ▁principles : ▁ ▁Princi ple ▁ 1 : ▁No ▁action ▁taken ▁by ▁law ▁enfor cement ▁ag encies , ▁persons ▁employed ▁within ▁those ▁ag encies ▁ ▁or ▁their ▁agents ▁should ▁change ▁data ▁which ▁may ▁subsequently ▁be ▁re lied ▁upon ▁in ▁court . ▁ ▁Princi ple ▁ 2 : ▁In ▁circumstances ▁where ▁a ▁person ▁finds ▁it ▁necessary ▁to ▁access ▁original ▁data , ▁that ▁person ▁ ▁must ▁be ▁compet ent ▁to ▁do ▁so ▁and ▁be ▁able ▁to ▁give ▁evidence ▁explaining ▁the ▁relev ance ▁and ▁the ▁ ▁imp lications ▁of ▁their ▁actions . ▁ ▁Princi ple ▁ 3 : ▁An ▁aud it ▁trail ▁or ▁other ▁record ▁of ▁all ▁processes ▁applied ▁to ▁digital ▁evidence ▁should ▁be ▁ ▁created ▁and ▁preserved . ▁An ▁independent ▁third ▁party ▁should ▁be ▁able ▁to ▁examine ▁those ▁processes ▁and ▁ ▁achieve ▁the ▁same ▁result . ▁ ▁Princi ple ▁ 4 : ▁The ▁person ▁in ▁charge ▁of ▁the ▁investigation ▁has