A court in the Turkish city of Kayseri has began to hear key testimonies in the trial of eight men, including four policemen, accused of beating a teenage student to death during anti-government protests last year.

Ali Ismail Korkmaz died after being pummelled with baseball bats and truncheons in the western city of Eskisehir on June 2, one of eight people to die during three weeks of protests that convulsed the country.

"I saw Ali Ismail being kicked on his back and head again and again," Semih Berkay Yapici, a witness who was on the scene, told the court on Monday.

"He lost his balance, fell on the ground, hit his head on a stone and lost consciousness. His eyes were closed."

Yapici said once Korkmaz regained consciousness he was again kicked on the head and as he fled his attackers, was set upon by plainclothes policemen with gas masks who ruthlessly kicked and beat him on the legs.

"He then took a turn and went out of my sight ... his face is etched into my memory," he said.

Yapici identified the police suspects who attended the proceedings in handcuffs from mug shots.

During the attack, which was recorded by security cameras, the 19-year-old student, who was wearing a "World Peace" T-shirt, suffered a brain haemorrhage and died after 38 days in a coma.

Eight men, including four plainclothes policemen, are accused of premeditated murder and face between 10 years and life behind bars if convicted.

During the first hearing of the case in March, the four police officers denied beating Korkmaz to death.

An expert report analysing mobile phone signals, which was published in local media this month, suggested the suspects may have been in the same area as Korkmaz on the day of the incident.

Karasu said that new evidence and witnesses' testimonies would determine the course of the case.

Authorities moved the trial nearly 360km east of Eskisehir to Kayseri in a bid to avoid fresh trouble.

Protests are expected on Monday to coincide with the second hearing, despite tight security measures.