The L.A. County Sheriff's Dept. opened the door -- literally -- to a gunman who pumped 7 bullets into Suge Knight's body ... and his lawyer says it's all a sinister, shocking conspiracy.
Suge's new lawyer, Thaddeus Culpepper, filed legal docs in which he alleges a Sheriff's deputy was working a venue -- 1 OAK in WeHo -- for the 2014 VMA weekend when he let the shooter inside the club.
According to the docs, surveillance video clearly shows Deputy Henry Boyd letting the gunman inside the club, shortly before shots rang out.

