Rome, March 29 - The secretary general of police union Silp Cgil has distanced himself from colleagues who staged a protest in the northern Italian town of Ferrara outside the office of the mother of an 18-year-old man who died in police custody in 2005 with four officers later convicted of his manslaughter. ''After all our battles to democratize the police force, and after the tragedy a mother and a family has gone through, it is discomforting to see what was organized in Ferrara by the Coisp police union'', said Daniele Tissone. ''Sentences, particularly if they are definitive ones, need to be respected''. Tissone's is the last in a series of public denouncements of the protest that took place on Wednesday outside the city offices where Patrizia Moretti, the mother of Federico Aldrovandi. The demonstration sparked a national outcry from fellow officers, government officials and civil society alike. Two dozen Coisp police union members staged the protest in solidarity with the four officers convicted of Federico's manslaughter on September 25, 2005. The teenager, who was stopped on his way home after spending Saturday night with friends, died of asphyxia after police used excessive force to restrain him, sitting on his chest. Aldrovandi's family is now suing the police union secretary and a Senator for defamation following the protest.