Mean King Riddle

[paklover]

A king decided to let a prisoner try to escape the prison with his life. The king placed 2 marbles in a jar that was glued to a table. One of the marbles was supposed to be black and one was supposed to be blue.If the prisoner could pick the blue marble he would escape the prison with his life. If he picked the black marble he would be executed. However the king was very mean and he wickedly placed 2 black marbles in the jars and no blue marbles. The prisoner witnessed the king only putting 2 black marbles in the jars.If the jar was not see-through and the jar was glued to the table and that the prisoner was mute so he could not say anything how did he escape with his life?