The lawyers joined the mother of 22-year-old Noel Polanco on Saturday at the Harlem headquarters of the Rev. Al Sharpton.
They criticized Thursday's decision by a Queens grand jury not to indict the detective.
Detective Hassan Hamdy shot Polanco on Oct. 4 following a traffic stop on the Grand Central Parkway near LaGuardia Airport.
Hamdy's lawyer says the detective fired after Polanco reached under his seat. Polanco's supporters dispute that account.
Polanco's mother, Cecilia Reyes, cried and said she would keep fighting for justice.
Lawyer Michael Hardy said the family's attorneys are also pursuing civil actions against the city over the killing.
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