Picture Me Rollin' All Eyez on Me 2Pac

free like O.J. all day

OJ was found not guilty of murdering his wife. Therefore he was free
"Free like OJ" refers to OJ Simpson's acquittal in his highly publicized mid-90's trial for murder. He got off with no jail time, therefore Pac is referring to OJ as a free man
O. J. (Simpson) was acquited, though everyone knew he was guilty. You can't pin crimes on this badass