Raising latent fingerprints on paper isn't the sure thing depicted on all those cop shows, and in the real world, this bank robber has yet to leave a useful clue.

Blood tests give useful clues but don't prove anything one way or the other.

Strontium isotopes served as the most useful clues in determining the geographical histories of the specimens.

Looking back can provide useful clues too.

Items not specifically mentioned may provide much more useful clues.