Police officer Jason found guilty of killing Laquan McDonald four years ago

Chicago police officer Jason Van Dyke has been found guilty of second-degree murder in fatally shooting black teenager Laquan McDonald four years ago.

Jurors reached the verdict on Friday for the high-profile trial as Chicago Police enhanced their presence in the city, bracing for possible protests and even violence in case of a not guilty outcome, Xinhua news agency reported.

Learning the verdict, demonstrators erupted in cheers outside the courthouse, chanting, "Justice for Laquan. Justice for Laquan".

White police officer Jason Van Dyke shot 17-year-old McDonald 16 times in 2014, which triggered racial tension for years in Chicago, the third largest city in the US.

McDonald reportedly broke into a truck on the night of October 20, 2014, and Jason Van Dyke was one of the police officers dispatched to the scene. McDonald carried a knife but walked from police when Van Dyke fired 16 shots into the teenager, the police car's dashcam video showed.

The jury reached the second-degree murder verdict instead of first-degree, which means they found the officer believed his life was in danger at that time but the belief was unreasonable and his reaction was unjustified.

Jurors told media later that the officer's claim of self-defence did not match video footage and they could not buy it.

Second-degree murder carries a sentence of 4 to 20 years, said special prosecutor Joseph McMahon, who called the verdict "gratifying" and justice for Laquan McDonald and his family.

Van Dyke was also found guilty of 16 counts of aggravated battery with a firearm.

"The end of this trail offers an opportunity for this city to come together," McMahon added.

However, Van Dyke's lead attorney, Daniel Herbert, said he wasn't surprised by the verdict and vowed an appeal on the judge's refusal to move the trial outside Cook County because of the extensive pre-trial publicity.

He argued that it was "a sad day for law enforcement."

Hundreds of people marched along the main avenue in downtown Chicago after the verdict, interrupting traffic. But the demonstration remained peaceful so far.

(With inputs from agencies.)