(Refiles to cut extraneous text)
By Caroline Stauffer
SAO PAULO, April 3 (Reuters) - A Brazilian court has sentenced 15 police officers to 48 years in prison each for their roles in the deaths of four inmates in the bloody crackdown of a 1992 prison riot that left 111 people dead.
Known as the Carandiru massacre after the now-closed prison where it unfolded, the incident is one of the darkest chapters in Brazil's struggle to improve conditions in overcrowded penitentiaries and to ensure police obey the law.
The sentences, handed down late Wednesday by a state court in Sao Paulo, were the latest stage in legal proceedings that have been mired by more than two decades of controversy, bureaucracy and other delays.
A first round of sentences was handed down a year ago, and a total of 73 officers were sentenced to varying jail terms in four stages of trials. None of the officers has yet gone to prison and all are expected to appeal.
"With this decision comes an end to the trying of one of the most complex cases in history," the Sao Paulo court said in a statement on Thursday.
President Dilma Rousseff, who was jailed in the early 1970s for fighting against the country's military dictatorship, hailed the sentences as a sign that Brazil was working to end impunity for human rights abuses.
The Carandiru massacre occurred in October 1992, when military police in São Paulo, Brazil's most populous state, stormed a four-story jail to quell a fight between inmates. Police fired more than 300 rounds at the prisoners, members of rival gangs who had begun fighting during a soccer game.
Some of the inmates were killed by other inmates. No officers died during the massacre.
In the ensuing years, investigators have worked to piece together what exactly happened in the prison and assign blame. Dozens of police officers were arrested and charged with homicide and other crimes.
In the trial, which began last April, prosecutors argued that officers, most now retired, executed the prisoners in their cells even when they surrendered. Defense attorneys said the officers acted in self-defense.
The sentences handed down for the officers, in some cases hundreds of years in prison, are largely symbolic because no one in Brazil serves more than 30 years in jail.
Carandiru prison was demolished in 2002 and was the subject of a hit film in 2003.
Human rights groups saluted the sentences as a milestone in a long-standing battle against police impunity in Latin America's biggest country.
"This sends an important message to public security forces in the state of São Paulo and throughout Brazil that nobody is above the law," said Maria Laura Canineu, director for Human Rights Watch in Brazil.
Despite a recent decade of economic growth, and increasing global attention over its hosting of the 2014 soccer World Cup and the 2016 Summer Olympics, Brazil's police and penal system continue to face accusations of human rights abuses.
Its police forces, many of whom still maintain military structures left over from the military dictatorship that ended in the 1980s, have a reputation for illegally pursuing and punishing criminal suspects.
While authorities have successfully cleaned up some of the forces, renegade police are still routinely involved in petty corruption, drug trafficking, kidnappings, murder and other illegal activity.
Many of the country's penitentiaries, meanwhile, remain nightmarish facilities where crowds of unsupervised convicts are crammed into cells designed for far fewer prisoners.
Earlier this year, officials in the northeastern state of Maranhão came under fire for a series of violent incidents within its penal system. In addition to a video from one prison in which convicts celebrate the beheading of three inmates, investigators discovered that wives of some inmates were raped during visits. (Editing by Paulo Prada and Paul Simao)