Police and city leaders have denied a cover-up. Police Commissioner Charles Ramsey and Mayor Michael Nutter have said officers pursued the car driven by Hall after a triple shooting in the city's Feltonville section.
The three men are charged with attempted murder and other counts related to the shooting.
The Rev. Al Sharpton, a civil-rights activist, has suggested the beating was racially motivated and called it "worse than Rodney King," referring to a black man beaten by white Los Angeles police officers after a 1991 traffic stop.
Ramsey dismissed Sharpton's comments but conceded the incident has given the department a "black eye."
Sharpton is scheduled to meet Sunday with Dyches at the Philadelphia jail.
Thirteen officers have been taken off street duty as police investigate the beating, which was captured on videotape by the local Fox affiliate.