a mixed record, representing the state against large-scale land proprietors, but also taking work from the latter (who included some of the most powerful politicians in the state). His interest in the tangled difficulties surrounding land titles in Maine prompted him to write a seminal work on the subject in 1801, The History of Land Titles in Massachusetts. The two cases with the highest profile that Sullivan prosecuted while attorney general were both criminal cases. In 1801 he prosecuted the Dedham murderer Jason Fairbanks, who had retained Federalist Harrison Gray Otis as his defense council. Fairbanks was convicted of murdering a local woman, but escaped after his conviction, and was eventually captured near the Canada–US border and hanged. Sullivan and Otis faced off again in 1807 in the sensational trial of Thomas Selfridge, accused of murdering Charles Austin. Selfridge, an older Federalist attorney, had been retained to assist in the collection of a debt from Austin's Republican father. In the politically charged atmosphere of the day in Boston, Selfridge, fearing for his own safety, had armed himself with a dueling pistol. The younger Austin had, apparently on his own initiative, sought to beat Selfridge with a cane, and Selfridge fatally shot him in the encounter. Selfridge was defended by a cadre of Federalist lawyers including Otis and Christopher Gore, and was acquitted of murder by a jury whose foreman was Patriot and Federalist Paul Revere. Sullivan continued to take private legal work even while he served as attorney general. In a career spanning more than forty years, his law practice was among the largest and most successful in the state. He was an acknowledged expert on admiralty law, and is described by legal historian Charles Warren as one of the most important legal figures of the time in Massachusetts. Maine–New Brunswick border commission In 1796 Sullivan was appointed by Secretary of State Timothy Pickering to be the United States agent to the binational commission established under the terms of the Jay Treaty to formalize the border between Maine and the British (now Canadian) province of New Brunswick. The southern portion of the border had been defined as the Saint Croix River in the 1783 Treaty of Paris, which ended the American Revolutionary War, but there was some question as to which river it actually was because the area was then sparsely peopled and poorly surveyed, and maps of the area