Selection from a legal notebook kept by William Cushing, the chief justice of the Supreme Judicial Court of Massachusetts, regarding the case of Quock Walker (1783).  The jury found in favor of Walker, an enslaved person who ran away from his master, Nathaniel Jennison, in 1781.  Walker's case rested on the fact that his former master had promised to free him at age 25, a promise which Jennison had ignored.  Cushing went even further, writing that "there can be no such thing as perpetual servitude of a rational creature."  When the judge gave his instructions to the jury, he explicitly declared slavery incompatible with the new Constitution of Massachusetts.  Although this case did not immediately emancipate every enslaved person in the state, it did mark the end of slavery as a legal practice in Massachusetts.