For the moment, I am entertaining the possibility that this report is accurate (who knows, right?). Meaning, that the results of some type of analytical testing has yielded the conclusion, that this is post mortem DNA. I will speculate that, the DNA sample was/included cellular material, that may exhibit certain changes, post mortem. The DNA sequence is not what suggests the "post mortem state", but rather the cellular material from which the DNA is obtained.
Examples might be: liver, kidney, pancreas, heart tissue, etc.
I read a UK newpaper, absolutely go on a rant about how this is obviously a ridiculous frame up, bla bla bla - as everyone knows that DNA sequencing does not/cannot determine a living vs. a dead person. How lame was that. They conveniently did not address the fact that certain types of cellular material may, indeed, suggest a post mortem state. At that point, I came to the conclusion that the UK papers have an obvious agenda.