Someone is threatening to kill Casey Anthony, her lawyers, and the jurors who found her 'not guilty' of murdering her daughter -- this according to Casey's attorney Cheney Mason.
Mason tells TMZ his team has been receiving "all kinds of threats" at his office since the controversial verdict came in ... including "one we just turned over to law enforcement."
There are reports Casey's parents are also being targeted and have gone into hiding.
For his part ... Mason doesn't seem worried. He laughed off the threats claiming the people behind them are simply "cowards."