Citizens throughout Toronto fear for their safety if they co-operate with police after dramatic messages and overt attacks — including bullets being left on the doorsteps of witnesses and drive-by shootings through their windows, a police expert told court Wednesday. "There is nothing nice about the code of silence at all," Sergeant Gavin Jansz, a Toronto police officer, testified at the murder trial of a man accused of shooting dead a Crown witness who previously had fingered him in another shooting. The code of not co-operating with police has evolved and spread from just being an unwritten rule among criminals, he said. "It's been promoted into an overt phenomenon where people in our community accept and adhere to this message for a number of reasons," said Sgt. Jansz. "It has become quite dramatic." Sgt. Jansz was qualified Wednesday to provide the court expert evidence on both the code of silence and urban street language at the first-degree murder trial of Lamar Skeete, 21. Skeete, also known by the nickname Ammo, stands accused of the execution-style shooting of Kenneth Mark. The 30-year-old victim had worked to curb guns and gangs in his west-end Toronto neighbourhood. It was a stance that allegedly led to him being shot in the back; he survived and fingered Skeete and his brother, accusations that fell apart in court. On Dec. 29, 2009, shortly after the Skeete brothers were released despite the victim's testimony, Mark was shot once in the head and died. The Crown alleges it was a retaliatory act by Skeete. Sgt. Jansz's evidence was of a general nature, not acts specific to the shooting of Mark. He said some neighbourhoods in the city were particularly "terrorized" by the code of silence but it is experienced city-wide. Otherwise good citizens are reluctant to be witnesses or come forward with information to help police investigate crime out of fear, said Sgt. Jansz. Prosecutor Karen Simone asked him what the concern was by the residents. "Their own personal safety or the safety of members of their family," he replied. Criminals accomplish this "either by instilling fear or taking physical measures to shut that person up. "If I leave a bullet on your doorstep, that sends a message," he said. "There are also more explicit ways — shootings, drive-by shootings into somebody's window, is an example." The jury trial before Ontario Superior Court Judge Ian Nordheimer continues Thursday.