I am copying a post of mine from the PI/photo thread:
Nuclear DNA is more comprehensive than mtDNA and can distinguish betwen Casey and Caylee while mtDNA cannot. As has been stated many times before mtDNA was used to test the hair in the trunk. (hence the many arguments we hear that since Casey is alive, the hair must have belonged to Caylee) Why did they not use the more inclusive nuclear DNA testing? It is MY OPINION, since we have no evidence whatsoever that the sample was degraded, that they performed mtDNA
because there was no root attached, which you need to have in order to perform nuclear DNA testing. If there was no root attached, ipso facto they
did not find a postmortem root band.
Post-mortem banding occurs within 1 mm of the root. In fact, it's properly called "post-mortem root banding". This phenomenon will not occur if the hair has come away from the scalp of a decedent shortly after death.
http://www.aafs.org/pdf/Seattleabstracts06.pdf
If the hair root has tissue attached, Nuclear DNA analysis; If there is no tissue and/or root, Mitochondrial DNA analysis.
www.ct.gov/dps/lib/dps/Mitochondrial.pdf.ppt