throw (oneself) on/at the mercy of (someone)
To plead with someone, especially a figure of authority, to show one lenience and mercy. I have no excuse for what I did. I can only throw myself on the mercy of the duke and beg for his forgiveness. She threw herself at the mercy of the court, saying that her dependence on drugs led her to commit those crimes.
throw oneself at the mercy of some authority
and throw oneself on the mercy of some authority; throw oneself (up)on someone's mercyFig. to seek mercy from a court of law, especially at one's sentencing for a crime; to seek help from an official or institution. He pleaded guilty and threw himself at the mercy of the court. It did no good to throw myself on the mercy of the State Department. Please don't! I throw myself upon your mercy!