It might. But personally, I expect the jury to concentrate on the kidnap/murder, and treat the child porn as an extra charge. If they find him innocent of the kidnap/murder, they'll probably find him innocent of the porn too, just as a slap in the DAs face. If they find him guilty, they'll probably through in the porn too, since it's hardly worth arguing about at that point.
So, in the end, I don't think the porn will weigh heavily. Of course, I note they have called to examine the evidence, so maybe I'm just engaging in wishful thinking.
Drew Garrett