Episodic television in general isn't really a good medium for mystery stories. Watch any random network police procedural, and the murderer can usually be figured out by picking out the most recognizable name in the guest cast, or sometimes there's a character the detectives chat with near the beginning who doesn't show up again until near the end, at which point it's guaranteed to be because they are the murderer. Sometimes that character is the recognizable guest star, thereby making their guilt obvious. I've even heard there are some situations where the producers are pursuing a particular actor to guest star on the show, and they actually mandate the only way they'll agree is if they get to play the murderer.
For example, I had such an experience watching an episodes of The Commish, (1991-1960) . in the episode "Nothing to Fear but Fear..." I immediatley decided who the perpetrator was as soon as I saw the actor. Was it an actor who played villains all the time? No, I had only seen that actor portraying good characters before. But that actor had been listed as one of the guest stars in the opening credits but hadn't shown up until a scene where the perpetrator was likely to be in.