A young man with an "unhealthy obsession" with violence stabbed his two friends to death with a hunting knife near their home, a court heard.
Steven Bayliss and Nuttawut Meechao died in 2005
Thomas Palmer was 18 when Steven Bayliss, 16, and Nuttawut Meechao, 14, were killed in Finchampstead, Berkshire, in September 2005.
Prosecutor Julian Boughon said it was a "straightforward case of murder".
Mr Palmer, from Blagrove Drive, Wokingham, pleaded not guilty to two murder charges at Reading Crown Court.
The court heard that the teenagers were socialising and drinking alcohol ahead of their first day at college the following morning.
But Steven, Nuttawut Meechao - known as T.Wood Nadauld - and Mr Palmer became separated at about 2000 BST.
Mr Bough told the jury that no-one knew exactly what happened next.
The bodies of the two boys were found in a field
A court heard Steven was attacked with "such ferocity that police who found his body believed that an attempt had been made to sever his head from his shoulders".
It was an injury that killed him almost instantly, but Mr Palmer continued to attack him with the 17 centimetre long blade, stabbing him five more times, the court heard.
Nuttawut, who had moved from Thailand a few years before, was stabbed in the chest and received more than 20 other wounds.
Police were alerted when Mr Palmer made a 999 call saying that "somebody has been cut a little".
But he claimed not to know what had happened and asked officers to take him back to the scene of the crime so he could help.
It was there that police noticed his hands and feet were covered in blood.
He had discarded his blood-stained sweatshirt and T-shirt earlier as he left the scene.
The court heard Mr Palmer initially claimed that he had been acting in self defence after Steven produced a knife himself.
But he later admitted that the blade was his.
The trial continues.