I'll have to go back and and see where this episode first revealed this case to be still unsolved, but with the way it was kind of dragging on at certain points, it was sort of evident even without any official reveal that this wasn't going to have any kind of resolution. Also, when they first brought up the detail of a direct familial connection with the DNA samples collected at the crime scene, there was probably only a little over 6 minutes left in the entire episode, from what I remember. Unless Casefile had decided to jump the gun and cover a case in which the defendant hadn't even gone through their trial yet, there was no way that person was the killer.
And maybe it's just personal preference, but I'd rather be strung along and then be told at the end that the case is still unsolved rather than be told it in the beginning. The storytelling aspect of true crime shows is a main reason why I and a lot of other people listen to them, so I like to be fully engrossed in an episode knowing that sometimes the cases won't have the resolution that we may want. But because I genuinely enjoy the experience of listening to all the details of a case, I'm willing to deal with the possible disappointment of a lack of closure afterwards. The end result can be frustrating sometimes, but it doesn't mean that just because of that, I didn't enjoy listening to the episode at all.