I pushed the Otterbox's screen cover out of the plastic inner case before I put the phone into the Otterbox. That was the only part of the Otterbox I did not like. So yes you can use the Defender case without their built in screen protector. Besides, the Otterbox screen cover is anti glare and makes the touch screen less sensitive.
Now, I put a clear screen protector from Verizon on the phone's screen before i stuck it in the Otterbox and the screen looks clear and crisp, while having an added layer of anti scratch protection.
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