An admissions officer at Caltech once told me they did look at applicants with poor grades and would overlook them if there was a good reason why the grades were poor and there was very strong evidence that the applicant was impressive anyway.
Yes, but you have to consider very carefully what "poor grades" means here. Coming from a Caltech admissions offices, "poor grades" is anything less than about a 3.8 (unweighted), or anything less than straight As in math and science.
Anything less is beyond poor compared to Caltech's admissions standards.
