The implication is that these isolated cases are on an imaginary list of things that are relevant to the current conversation. You can think of the present perfect as a kind of "diary tense". If you say, "The use of the cane has resulted in physical injury", you mean that the occurrence of such an incident is written down somewhere (in an imaginary diary).
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Anonymous"there HAVE BEEN isolated cases in the PAST"No. The present perfect is about things in the past. Don't let the name 'present perfect' fool you. The word 'present' tells us that the reference point is the present. The action itself is in the past.
Since its in the past, shouldn't we use "had been"??
AnonymousI thought the present perfectNo. You are mistaken. It is about a happening in the past. Trefersreferred to a happeningofin the present, and it is still taking place now.