Remember when 2 of this sons-in-law defected back in 1995...
taking their wives (Saddam's daughters) with them?* Odds are we got some good blood samples from those daughters during medical exams. If blood tests are good enough to establish paternity with over 99.9% reliability, then the same could be used for identification.
* Those two guys certainly deserved to win the Darwin Award that year. They were stupid enough to believe Saddam's promises of their safety, so the returned to Iraq. They were both murdered soon afterwards.