Besides the shape of the skull breakage, there are defense claims that the crime scene recovery and storage of DNA was botched. The state claims a fall down stairs is not what killed her. It’s reasons for homicide at Peterson’s first trial also didn’t agree with then defense expert Henry Lee regarding blood pattern (spatter) evidence.
It’s the Mike Peterson retrial in Durham NC. His first conviction was overturned in 2011.
More info on the case which originally was trie in 2003 from the source of truth and veracity. Wikepedia It gives a good chronology of this decades long process.