On February 12 , 1770 , he published in the '' Gazette '' a call to his countrymen " to break off all social intercourse with those whose commerce contaminates , whose luxuries poison , whose avarice is insatiable , and whose unnatural oppressions are not to be borne He used the signatures Mentor , Callisthenes , Marchmont Needham , Edward Sexby , & c. , in later letters to the '' Boston Gazette . '' After the Boston Massacre ( March 5 , 1770 ) he and John Adams defended Captain Preston and the accused soldiers and secured their acquittal . Prosecuting the case were Robert Treat Paine and Josiah 's older brother Samuel Quincy , who shortly after was named solicitor general
Boston Massacre
Boston Massacre
Josiah Quincy II