Police said that the man crawled onto the terrace of a family home and began masturbating. The strange behaviour, which was spotted by a female neighbour, came on the same day that two fires were set nearby.
Police spokesman Henrik Justesen told TV2 that the two things seemed awfully coincidental so police decided to check for a connection.
The masturbating man left a trace of his DNA on one of the terrace chairs and police were able to use that evidence to arrest him back in February and charge him with 14 counts of arson for fires in the Odense area in 2015 and 2016.
The man's trial began on Tuesday, with prosecutors saying that he had caused at least 25 million kroner worth of damages.
Justesen said that police were confident that they have found their man because the fires stopped after his arrest. He described the man as a loner “without much social contact”.
“They run around in their own circles. They don't take part in social media and they don't have large social circles but instead keep to themselves. That means that there are very few people who know much about who they are,” He said.