At the start of the trial in Berlin, the 21-year-old main defendant wiped away tears as the prosecution read out the charge of attempted murder.

The six other defendants, between the ages of 16 and 21, sat motionless as the prosecution charged that they had “malevolently and cruelly” attempted to kill a man.

On Christmas Eve the seven young men, six of whom are refugees from Syria, one of whom is from Libya, were caught on CCTV camera as the 21-year-old lit a tissue and placed it directly next to the 37-year-old Polish man’s head as he slept on a bench in a Berlin underground station.

The group then all ran into an underground train and left the scene.

The Polish man had a cover over his head and was using his rucksack as a pillow. Both rucksack and cover caught light and started to burn.

“Within seconds a huge fire could have broken out,” prosecutor Martin Glage told journalists during a pause in the proceedings. He added that tests done by investigators proved that the burning tissue had the potential to set the man's clothing alight.

Luckily passengers who got out of the train were able to put out the flames.

Six of the seven young men are now charged with attempted murder, while the seventh is accused of denial of help.

Glage accused the youths of accepting that their actions could have led to the 37-year-old “tortuously burning”. But he conceded to journalists that he did not believe that the youths expected their actions to lead to the man’s death, and said he was not calling for life sentences.

The 21-year-old’s lawyer said it was a “misrepresentation” to say that his client had freely accepted that the victim could die.

The young men are yet to make statements to the court. But the 21-year-old told police during interrogations that, while he did light the tissue, he did not know what happened to it.

In recent months there have been similar arson attacks on homeless people. In Hamburg a 49-year-old homeless man’s sleeping bag was set alight in April. In February meanwhile, the sleeping area of two homeless men was set on fire in a parking lot, also in the port city.