Two years after the end of the Revolution, in 1783, a court in Massachusetts tried a minor assault case that was to have wide repercussions. Jennison, indicted for assault against walker, justified the assault because walker was his slave. Chief Justice Cushing's opinion marked the influence of new American ideals and effectively ended slavery in Massachusetts. The case is a milestone in the elaboration and extension of freedoms in the new nation- process that, in regard to slavery, lasted through the Civil War.
.... As to the doctrine of slavery and the right of Christians to hold Africans in Perpetual servitude, and sell and treat them as we do our horses and cattle, that (it is true) has been heretofore countenanced by the Province Laws formerly, but nowhere is it expressly enacted or established. It has been a usage―a usage which took its origin from the practice of some of the European nations, and the regulations of British government respecting the then Colonies, for the benefit of trade and wealth. But whatever sentiments have formerly prevailed in this particular or slid in upon us by the example of others, a different idea has taken place with the people of America, more favorable to the natural rights of mankind, and to that natural, innate desire of Liberty, which with Heaven (without regard to color, complexion, or shape of noses-features) has inspired all the human race. And upon this ground our Constitution of Government, by which the People of this Commonwealth have solemnly bound themselves, sets out with declaring that all men are born free and equal----and that every subject is entitled to liberty, and to have it guarded by the laws, as well as life and property―and in short is totally repugnant to the idea of being born slaves. This being the case, I think the idea of slavery is inconsistent with our own conduct and Constitution; and there can be no such thing as perpetual servitude of a rational creature, unless his liberty is forfeited by some criminal conduct or given up by personal consent or contract... Verdict Guilty.