Koivunen repeatedly changed his story under questioning. He denied killing the girls or even meeting them. However, he had transported four women in the summer, denying they were the same girls. In one of the interviews, Koivunen admitted to having met Metsänikula at the shore of Myllylampi, and that they talked about her studies and personal life over coffee. He also noted that Metsänikula used a lot of medication. As they continued their journey, the girl suffered a respiratory attack, causing Koivunen to stop and flee from the car. After returning, he found Metsänikula lying dead in the car's back seat. He later hid the girl's body in the Ingå forest. Similarly, Koivunen denied knowing anything about Laiho and Raijas, but changed his story and claimed to have met Laiho earlier and began a relationship with her. According to him, Laiho proposed a meeting and brought along Raijas, whereupon the three headed for Hyvinkää. While they drank at a nightclub, an unnamed younger man joined them and Raijas began vomiting. Koivunen claimed that the girls were murdered outside of his presence and that the unnamed man had admitted to battering them to death. Koivunen's wife was also interviewed, and told police that Koivunen came home on the night of 15 August and told her that he had shown two girls and a boy around the city. When he and his wife read the magazine about the disappearance of Laiho and Raijas, Koivunen noted that they looked the same as the girls he had been with. Koivunen's story soon changed again, removing the unnamed young man from his story. This time he claimed that the girls had fallen asleep on the back seat while he was driving. Upon awakening, Koivunen noticed that the engine was running, and tried to wake the girls, unsuccessfully. Shuddering, Koivunen wandered around hoping the girls would wake up, but they were dead. In fear, he remembered what had happened to Metsänikula one month earlier. Koivunen feared to get sent back to jail and decided to get rid of the bodies. When the police asked how they had died, Koivunen told them that while they slept, someone had dug up the hose from the car's back and connected it through the exhaust pipe to the back of the car. However, the question arose of how Koivunen survived that. Koivunen never acknowledged his guilt and changed the details of the story many times, remaining consistent about a few details. According to his wife, the girls were scared, and had vomited and choked while in the car. When they heard that the police had found tire marks on the fringes, Koivunen's wife remembered her husband's strange and nervous behaviour on that night. During the investigation, a hair of Koivunen was found on Laiho and Raijas' bodies. The camera found at home was also identified as his, as well as fingerprints from a photo found in a back alley near his home. There were plenty of anonymous tips, some of which were significant. During a preliminary investigation, a girl told the police that she had hitchhiked from Helsinki to Hyvinkää. The driver was a 41-year-old male. At first, everything seemed innocent until the man had decided to introduce the girl to the city. He had taken her, among other places, to the
Taabor mountain, speaking about himself and his life on the way. When they got there, he did not let the girl out and threatened her, but she jumped out of the car and fled. After the incident, she had seen that same man near her house several times. When she was shown a picture of Koivunen, she immediately recognized him. == Trial ==