A 22-year-old Turkish waiter was found guilty of murdering two women from Northern Ireland in August 2011.
Recep Cetin was sentenced to life in prison, and his father, Eyup, was found not guilty and walked free.
The two friends, Marion Graham, 54, from Newry, and Cathy Dinsmore, 53, from Warrenpoint, were found stabbed to death in a forest overlooking the port city of Izmir. They both suffered multiple stab wounds.
The two victims, along with Graham’s daughter Shannon, were holidaying in the popular resort town of Kusadasi.
Cetin was working as a waiter and dating Shannon, who was 15 at the time. He claimed to be a teenager, however medical tests after the killings revealed he was in his twenties.
He claimed in court he committed the murders under "heavy provocation." He said he acted in self defense.
His father had denied being involved and said he would have tried to stop the murders if he had been aware of his son's plan.
Three judges at the Izmir Bayrakli Fifth High Criminal Court found Cetin guilty of aggravated murder.
Members of the victims' familes traveled to Izmit for the court hearing.
George Dinsmore, brother of one of the victims, said he was happy with the outcome and hoped it would bring closure.
Shannon Graham, now 17, said she was "satisfied with the result" of the trial.