According to the witness, prostitutes were sent from Estonia to Helsinki and were given flats and Aarnio was behind this, said the witness.
The witness stated that Aarnio also brought anabolic steroids from Estonia into Finland and was involved in drug sales.
The witness claims not to have participated in the activities, but having heard of them from friends.
Instead, the witness told of inheriting an extortion racket from bars until Aarnio was, according to the witness, commanded to stop the operations.
The prosecutor is demanding a 13-year sentence for Aarnio.
Aarnio, however, has denied all charges.