The murder took place at Joutseno in Lappeenranta in October of last year.
The verdict said that the allegations brought against the convict were proved beyond doubt.
In Addition to the murder, the man was convicted for aggravated rape and grave breach of peace.
According to the court's public report, the act was intensely violent.
The man was also convicted for the sexual abuse of a child. According to the court's report, the convicted raped another 12-year-old in 2013.
