He has a BA from Harvard University, was a Community Fellow at Massachusetts Institute of Technology, and was awarded an honorary Associates of Arts degree from Roxbury Community College. Prior to his incarceration, he lived in the Roxbury neighborhood of Boston with his wife Terri.
Turner has worked as an activist since the 1960s. He has served as the director of a community development corporation, an organizer training center, co-founder of the United Community Construction Workers, and founder of the Boston Jobs Council.
He has also worked as Coordinator of Training at Emerge, a batterer's counseling organization, and as education director at a nonprofit consulting firm focused on establishing worker cooperatives.
He played an instrumental role in the formation of the Boston Workers Alliance.
Turner represented District 7, which includes Roxbury, Fenway, and the South End on the Boston City Council. He won his seat by a 693-vote margin against the city's director of youth services, who was the preferred candidate of Mayor Tom Menino.
Turner has a volatile relationship with the Boston City Council. First elected in 1999, Turner vice-chaired the Education and Human Rights & Services committees. He was a member of the Arts, Film, Humanities & Tourism, Education, Government Operations, Housing, Human Rights & Services, Post Audit & Oversight, Special Committee on Federal, Stimulus Oversight, Whole, and Youth Affairs committees until he was ousted by fellow councilmen after his criminal conviction. In February 2004, angry at being removed from the Education Committee, he compared City Council President Michael F. Flaherty to Louise Day Hicks, an opponent of the city's desegregation busing. He had also accused limits placed on debate as being "institutional racism".
He had some notable successes: In 2002, he authored an ordinance protecting transgender persons from discrimination that was overwhelmingly approved by the council and signed into law. Also, when Governor Mitt Romney tried to end the state's affirmative action guidelines, Turner became one of its aggressive critics, helping to lead the governor stop the change.
In April 2004, Turner was quoted by the Boston Herald as saying that Condoleezza Rice working for George W. Bush was "similar in my mind to a Jewish person working for Hitler in the 1930s."
In May 2004, Turner and activist Sadiki Kambon held a press conference to reveal photos purportedly showing US soldiers raping Iraqi women. The pictures were eventually identified as fakes, but only after four of the alleged rape shots appeared in a Boston Globe photo of the two men. Turner was subjected to wide criticism from conservative media and was censured by six members of the City Council. Turner was unrepentant, noting that he had urged the media to confirm the photos’ authenticity before disseminating them.
On August 3, 2007, Turner was videotaped by FBI informant Ronald Wilburn, accepting $1,000 cash from Wilburn in Turner's district office in exchange for pushing for a liquor license for the Roxbury nightclub Dejavu. On November 22, 2008, Turner was arrested and charged with attempted extortion under color of official right.
On December 9, 2008, Turner was indicted by a federal grand jury on three charges of making false statements and a charge of conspiracy with former State Senator Dianne Wilkerson, all stemming from an FBI public corruption investigation. Turner was found guilty of the false statement and bribery charges by a jury on October 29, 2010.
Turner has made claims that both he and Wilkerson are victims of a government conspiracy against African-American officials.
On December 1, 2010, Turner was expelled from the Boston City Council by an 11-1 vote making him the first council member to ever be expelled in the history of the modern Boston City Council.
On January 25, 2011, Turner was sentenced to three years in prison. He was released early for good behavior in July 2013, after serving 28 months.