According to the "Weather Underground" archive, the last measurable precipitation at the Baltimore airport prior to 04 Dec 04 was a half-inch of rain on 01 Dec 2004, with the temperature for the next three days oscillating between roughly 30F and 50F, averaging above freezing.
I'd bet more than one beer that the folks at the weather office at the Baltimore Airport keep pretty accurate records.
I'll concede it's possible the accident occurred early in the morning, with frost on the road, but that would pretty much require that they were just about the first vehicle out in the morning on that road that day.
Or it could be that whoever was driving wasn't paying attention and missed a turn and claimed "black ice" to assuage their guilt over nearly killing two of their kids.
A-little-more-background-on-the-car-crash ping.
I think your onto something, looking at the Dec 4 2004 link;
http://www.wunderground.com/history/airport/KBWI/2004/12/4/DailyHistory.html
it was a fairly nice day, calm winds, with various partly cloudy to mostly cloudy during the afternoon hours. That Rain on the Dec 1 2004 seems to have ended by 10:54 am, so it had the better part of 3 days to dry up.