"Our own source, who had been able to reach al-Baghdadi, brought al-Baghdadi's underwear to conduct a DNA test and make sure (100%) that the person in question was al-Baghdadi himself," Polat Can, a senior advisor to the Kurdish-led SDF, said.

from Times of India https://timesofindia.indiatimes.com/world/middle-east/syrian-democratic-forces-say-baghdadis-underwear-was-dna-tested-before-raid/articleshow/71799331.cms