▁in ▁viol ation ▁of ▁the ▁Four th ▁Am end ment ▁could ▁not ▁be ▁used ▁in ▁federal ▁criminal ▁proceed ings . ▁In ▁an ▁opinion ▁written ▁by ▁Justice ▁William ▁R . ▁Day , ▁the ▁Court ▁reason ed ▁that ▁the ▁Supreme ▁Court ▁had ▁a ▁constitution al ▁duty ▁to ▁ensure ▁federal ▁courts ▁ex cluded ▁il leg ally ▁obtained ▁evidence : ▁ ▁Over ▁the ▁next ▁several ▁dec ades , ▁the ▁Court ▁generally ▁held ▁that ▁this ▁" ex clusion ary ▁rule " ▁only ▁applied ▁to ▁cases ▁in ▁which ▁federal ▁officers ▁were ▁involved ▁in ▁the ▁illegal ▁searches ▁and ▁se iz ures . ▁▁ ▁In ▁ 1 9 4 9 , ▁the ▁Court ▁confront ed ▁the ▁issue ▁of ▁the ▁ex clusion ary ▁rule ' s ▁application ▁to ▁states ▁in ▁the ▁case ▁of ▁Wolf ▁v . ▁Colorado . ▁The ▁Court ▁survey ed ▁contempor aneous ▁U . S . ▁states ▁and ▁found ▁that ▁although ▁ 1 7 ▁states ▁had ▁adopted ▁the ▁ex clusion ary ▁rule ▁of ▁We eks ▁in ▁their ▁own ▁state ▁law , ▁ 3 0 ▁others ▁had ▁rejected ▁it . ▁It ▁therefore ▁concluded ▁that ▁it ▁was ▁not ▁a ▁" de part ure ▁from ▁basic ▁standards " ▁of ▁due ▁process ▁to ▁allow ▁states ▁to ▁introduce ▁il leg ally ▁obtained ▁evidence ▁in ▁state ▁tri als . ▁For ▁the ▁next ▁ 1 2 ▁years ▁until ▁M app , ▁the ▁Court ▁did ▁not ▁apply ▁to ▁the ▁ex clusion ary ▁rule ▁to ▁evidence ▁obtained ▁by ▁state ▁officers ▁and ▁used ▁in ▁state ▁courts ▁unless ▁co erc ion , ▁violence , ▁or ▁brut ality ▁was ▁involved . ▁For