Rapper Trinidad James -- Off the Hook For Weed Arrest

Trinidad James may have looked baked out of his mind in the mug shot after his arrest last week ... but pics don't convict ...so James is walking ... TMZ has learned.

James was busted Friday for possession of marijuana after lighting up in his Mississippi Holiday Inn hotel room -- but after further investigation, cops have backed off the case.

We asked repeatedly why they won't even present the case to prosecutors ... but we got nothin'.