IMO,pleading the blood Is saying that you are not guilty because GOD who loves righteousness accepted you through the finished work of JESUS and Instead of seeing your sin,HE sees the perfect sacrifice that JESUS made for us paying the price with HIS life shedding HIS blood.
The law says If you break It that you will pay with your life,LIFE Is In the blood.
Because of breaking GODs law In the garden law was added but people can’t measure up to fulfilling the law(GODs perfect standard of righteousness)because although they delight In the law of GOD after the Inward man they would see another law In their flesh/mind warring against the law of their minds and bringing them Into captivity to the law of sin which Is In their flesh.
Who shall deliver us from the body of this death.
We see JESUS who took our place as a man he fulfilled the law, By The Way ALL the law and the prophets are summed up In one word,love.
GOD IN CHRIST had mercy on all mankind and took the punishment that a righteous loving GOD required for breaking the law and gives grace to all who believe In the WORD of GOD.
A New Testament was put Into place.The law was Impossible for man to fulfill of his own strength,JESUS delivered us from the body of this death,now the Issue Is do you believe In the WORD OF GOD.