[3] A close friend of Governor Paul A. Dever, Byrne was mentioned as a candidate for a number of prominent positions, including Boston Police Commissioner.

[3] Byrne was chosen despite pressure to give the job to William J. Foley Jr., a fellow assistant district attorney and Boston City Councilor, or another well known political figure.

Following the murder of Andrew Puopolo, Byrne received the support of Mayor Kevin White and the Boston Redevelopment Authority and began a crackdown on the vice district.

[5][6] Byrne was also the lead prosecutor of the perpetrators of the Great Brink's Robbery, as the federal statute of limitations had expired and only state charges could be brought against the gang.

During the campaign, the Boston Finance Commission announced that Byrne had "misrepresented" the qualifications of a company in order to grant two no-bid contracts to a former legal aide.