The thing about clues is that they are obvious when you know the answer. If you are on the other side of the screen, they can be completely opaque!
Gumshoe favors the breadcrumb approach of each clue leading to the next, in a linear line. Finding the clues is automatic, the fun is in putting them all together and reaching the solutions. It can fall down horribly if players have the clue but derive the wrong meaning from it.
I think a better approach is to provide about 3 different avenues to explore. Once you know what conclusions you want the players to draw, from which they can solve the mystery, create about three clues for every conclusion.
If your clues are freestanding, you can drop them into the path of the characters regardless of how they choose to proceed. If you have three clues for each conclusion there is more chance of them reaching the conclusion that you need. It is nice to have a Plan A, B and C if needed.
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