Cheating on Homework

[_brady_]

I grade papers for a sophomore/junior level engineering class. I sometimes find some suspect homeworks where the student may be cheating. Should I point this out to the professor? On one hand I feel like just letting it go because if they constantly cheat it will probably come back to bite them in the ass in the future. On the other hand the class isn't overly difficult and they really shouldn't have to cheat, they're probably just being lazy.

For what it's worth the cheating in question is using a solutions manual from an old edition of the book.