I have read that non-binary people can have both male and female DNA. If both male and female DNA were found on the deceased, I'm sure both check mark boxes would be checked. Just sayin'
Mysterious Iron Age Burial May Hold Remains of Elite Nonbinary Person | Smart News | Smithsonian Magazine
For one, the headline of the article is erroneous. 'Non-binary' refers to gender. Sex is not Gender. In the case of genetic markings to determine sex, it would be concluded as either Male, Female, or Intersex.
Two, IMO, if the suspect has the genetic make-up of both male and female chromosomes (intersex), that test would have to be based on certain types of samples and certain types of testing would have to be done, and we don't know where the sample came from to begin with. Also, MOO, the wording from police or whoever would not be "The DNA of both a male and female" because, to me, that implies two people. Whereas the DNA of a single intersex person would be read as just that, one set of DNA.
I'm having a hard time explaining this, but ultimately my point is IF Intersex, the process in determining such is also difficult, thus not revealing it as black and white as "Male and Female DNA". MOO. Ouch, this hurts my brain! And likely neither here nor there.
ETA: If it helps to understand, the more common, albeit outdated, term for Intersex is "Hermaphrodite".
I couldn't decide on any one article to link, this stuff is intricate! So here is just a basic run down of forensic DNA.
DNA Mixtures: A Forensic Science Explainer