The clashes were some of the worst in the summit's history
The most senior police officials charged in connection with the handling of riots at the G8 summit in Genoa, Italy, in 2001 have been cleared.
A court in the northern Italian city sentenced 13 officers to prison and acquitted another 16.
There were cries of "shame" from the public as the acquittal of the police chief was announced.
The clashes were some of the worst in the summit's history. One protester died and hundreds of people were hurt.
This was the last of three major trials arising out of the rioting.
Charges ranged from beating protesters to planting evidence and conducting arbitrary searches.
The BBC's David Willey in Rome says many of the police officers on trial are still in service and some have even been promoted.
Two of them are currently holding high-ranking posts in Italy's anti-terrorism unit and in the secret service.
The prosecution had asked for sentences totalling more than 109 years but the sum was 35 years and seven months.
A key focus of the trial was a police charge into a school where protesters were staging an alternative summit.
Vittorio Agnoletto, a summit protest organiser and now an MEP, told Reuters news agency: "Today is one of the saddest days in the post-war history of the republic.
"From now on police chiefs who allow their men to smash the heads and the backs of people sleeping peacefully can be sure of impunity and the guarantee of a fine career."
But interior ministry undersecretary Alfredo Mantovano said the verdict showed the Italian police force was "healthy and deserves everybody's gratitude".