>> How about PO-lice, and DEE-troit? :-) <<
oh, PUHHHleeeze!
Seriously, CA, you make a good point: French words (and Police, Detroit, and Offense are all French words) create a difficulty: In French, syllables are accented evenly, or the unaccented syllable is subsumed entirely. Usually, in American English, we subsume the unaccented syllable (P'lice, D'troit, etc.). In certain regions, however, because such syllables are not incidental to the root word, the first syllable is emphasized (POHlice, DEEtroit, etc.)
In the case of offense and defense, however, I think the general rule is to subsume the first syllable. But under certain circumstances, including sports, I guess the first syllable is not subsumed, and, hence it is accented, so that it can be clearly heard.
For instance, in court, it's plain that a person represents a defense, whereas an action represents an offense, so we subsume the first syllable; the d'FENSE rests, but the ofFENSE doesn't.
In sports, the words are almost always spoken to delineate between the offense and the defense, hence, the first syllabe is usually accented.
I didn't hear one person at the Super Bowl refer to it as "Day-twaa" ;-)
SD