Why does Julia Gillard pronounce it daybree when it is clearly pronounced debris?

It is a simple fact that a great many Words in any language do not have a single pronunciation. There is usually no hard and fast rule for which pronunciation is correct. Furthermore, how one pronounces Words will vary depending on his or her country of origin, and the region from which they come within that country.

The Word "debris" should not be pronounced with an "s". If Ms Gillard wishes to pronounce it "day-bree" instead of "de-bree", there are no rules to say this is incorrect.