The court heard that all of them had been drinking at a house party the night before.
After the attack they returned to the house party.
It was then alleged that they took off their blood stained clothes, and another friend Artur Woszcxyna, then drove to St Bees and threw a bag with the clothes and shoes over a cliff.
Another man, Artur Skoczen is also accused of helping cover up the murder.
All the defendants deny the charges.
The trial is expected to take up to six weeks.
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The family of Christian Pay, who died on Friday after suspected substance abuse at a festival, have paid tribute to the Millom teenager.
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Christian Pay's family say he was "loved by all" and had "the heart of a lion". The 18-year-old died after falling ill at the festival.