Someone suggested these items shouldn't spawn unless you've triggered the appropriate quest path. I disagree. I think locating any of these items in the rooms of the various suspects can cause a clever player to take them to the dog before the dog even prompts them for these items. And that's pretty cool if/when it happens.
Except that's extremely piss poor and here is why:
What you're saying has nothing to do with clever or thinking or any of that. In fact it's not even possible to put those pieces together due to there being way to many variables involved.
1. You have to be made aware that these types of items are involved with the murder no matter. Which they are not.
2. You can only know if they're involved with a very precise and specific set up which if you do not do, (Which apparently a lot of people didn't) then all those items just become like everything else in the game you pick up...nothing more than regular items.
3. Things like this need to be consistent if they are not then there will be problems.
4. Now onto the dog, Unless it says right on the item FOR THE DOG or something like it, it is impossible to know enough to open up your inventory and have the dog interact with anything in it. Furthermore the petpal perk would be the only reason anyone would interact with the dog in the first place. So people that don't have the petpal perk can know the dog is trying to tell them something but that is clearly referencing that if you want to know what the dog has to say, then pick the petpal perk so you can talk with it.
5. Finally there are other aspects involved that wouldn't make any sense such as finding these items AFTER the murder is already solved or finding these items without the murder quest even active.
So as you can see what you said is very flawed and next to impossible to do because it requires a precision set up and execution and information you're not given that you MUST have.
