cast doubt on
cast doubt on (someone or something)
To cause someone or something to be viewed with doubt, skepticism, or uncertainty. I considered Walt for the promotion, but his constant lateness soon cast doubt on that decision. Such a significant error really cast doubt on all of the experiment's results.
cast doubt on
Cause something or someone to be questioned. For example, The prosecutor cast doubt on the wife's alibi. This idiom uses cast in the sense of "throw," a usage dating from the early 1200s.