White blood cells frequently infiltrate soft tissues in order to do their duty so it's quite plausible that some donor DNA sequence will be found in other organ

White blood cells frequently infiltrate soft tissues in order to do their duty so it's quite plausible that some donor DNA sequence will be found in other organs. I couldn't seem to find a link to the original report in the linked article however it would not surprise me if some of the forensic techniques replied on testing for mitochondrial DNA as it tends to be better preserved in the natural environment. Human cells are known to exchange mitochondria so mtDNA is more likely to display chimerism, especially in this case where the donor is matched to the recipient.